3 Proven Exhaust Upgrades for Real Horsepower Gains

Aftermarket exhaust advertisements often scream “+25 HP!” yet too often, the only thing that increases is the annoying interior drone on your daily commute. 

To separate hype from honest horsepower, we tested three axle-back systems under identical, controlled conditions. We installed them on the 2018-24 Toyota Camry, 2014-20 Infiniti Q50, and 2022+ Subaru WRX VB.

What did we find? Here’s the quick verdict:

• Best Performance: Subaru WRX VB (+9 HP / +8 lb-ft)
• Best Value: Infiniti Q50
• Best Sound: Toyota Camry Quad-Tip

Below, you’ll find the raw dynamometer numbers, detailed sound notes, and installation impressions. We also included a simple decision guide so you can upgrade your vehicle’s exhaust system once and do it right.

Our Vehicle-Specific Testing Methodology

To ensure our results were accurate and repeatable, we followed a strict protocol. This included dyno testing, road evaluation, and a quality inspection for each vehicle and exhaust system.

Dyno Protocol

All performance metrics were recorded on a Dynojet 424 chassis dynamometer. Each vehicle was fueled with 93-octane gasoline, and tire pressures were set to OE specifications. For each test, we performed two back-to-back runs with the stock axle-back and averaged the results for a baseline before installing the new unit.

Real-World Road Test

Dyno numbers only tell part of the story, so each car logged 300 miles of mixed driving. Sound levels were measured objectively with a dB meter and subjectively rated for tone and drone. We also clocked the installation time and inspected every weld, flange, and hanger for quality.

Quality Checklist

We verified the material of each system, confirming the use of 304 or 16-gauge stainless steel. We inspected the TIG-weld penetration for strength and consistency. We also checked for mandrel bends versus inferior crush bends and ensured all hardware was included.

Individual Product Reviews: A Deep Dive

We examined each of the three systems from Private Label MFG’s performance aftermarket exhaust collection to see how they performed on their specific platforms. Here are the detailed findings for the Camry, Q50, and WRX.

PLM Toyota Camry 2.5L/3.5L Axle-Back (2018-2024)

Image by Kevin Bonilla from Unsplash.
Alt text: Gray Camry parked in an industrial area.

Material: 16-gauge stainless steel | Tips: 3.5″ quad | Install Time: 1–2 hours

Dyno Results

• Stock 2.5L: 194 hp / 179 lb-ft
• PLM Installed: 199 hp / 183 lb-ft
• Gain: +5 hp / +4 lb-ft (2.5% increase)

Sound (7/10)

The Camry’s exhaust note transforms from anonymous to authoritative. It produces a deep baritone at idle that evolves into a lively bark above 4,000 rpm. There is a slight cabin presence at 75 mph, but it’s a pleasant hum rather than a headache-inducing drone.

Installation

The installation can be completed with jack stands and a 14mm socket. On the XSE trim, the rear diffuser requires a minor ¼-inch trim to provide clearance for the larger quad tips. The supplied gaskets sealed cleanly without any leaks.

Build Notes

The TIG beads are neat and consistent, and a look inside the pipes reveals zero slag, ensuring a smooth gas path. The system offers a choice of polished or burnt-blue tips to match your aesthetic preference.

• Pros: Most dramatic sound change; aggressive quad-tip look; noticeable 8 lb weight savings.
• Cons: FWD only, no AWD fitment; minor diffuser trimming required on some trims.

Best For: Daily drivers who crave an assertive sound and style upgrade without the cost of a full cat-back system.

Value Verdict: “If you want the Camry to sound as assertive as it looks, this is the sweet-spot bolt-on.”

PLM Infiniti Q50 Axle-Back (2014-2020)

Image by Ben Duke from Unsplash.

Material: TIG-welded stainless steel | Tips: 4.5″ slant | Install Time: 1–1.5 hours

Dyno Results

• Stock 2.0T: 232 hp / 255 lb-ft
• PLM Installed: 238 hp / 259 lb-ft
• Gain: +6 hp / +4 lb-ft (2.6% increase)

Sound (6/10)

This system delivers a refined, upscale burble that is pleasantly louder outside the car than inside. Highway drone is virtually absent, making it an ideal choice for commuters. It adds a sportier note without sacrificing cabin comfort on long drives.

Installation

This is a direct bolt-on to the factory mid-pipe on both RWD and AWD models. The hanger alignment was spot-on, requiring no adjustments. New hardware is included, making for a straightforward installation process.

Build Notes

The large 4.5″ slant-cut tips sit perfectly flush with the bumper line for a clean, purposeful look. The mandrel bends maintain a consistent 2.5″ diameter through the exits, promoting efficient exhaust flow.

• Pros: Lowest price of the trio; fully AWD compatible; subtle yet sporty tone that is neighbor-friendly.
• Cons: 2.5″ piping may limit peak flow for future big-turbo builds; tip design is more conservative.

Best For: Q50 owners wanting an upscale, non-intrusive growl at an affordable price point.

Value Verdict: “Dollar-for-dollar, this is the smartest first step before moving on to downpipes and tuning.”

PLM Subaru WRX VB Axle-Back (2022+)

Image from Private Label MFG.

Material: 304 stainless steel | Tips: 3.5″ staggered | Install Time: 15 minutes

Dyno Results

• Stock: 269 hp / 275 lb-ft
• PLM Installed: 278 hp / 283 lb-ft
• Gain: +9 hp / +8 lb-ft (3.3% increase) – the highest tested.

Sound (8/10)

This axle-back unleashes the classic Subaru thrum and makes the turbo spool much more audible. It’s aggressive on throttle yet surprisingly tame at cruise, with a cabin reading of just 79 dB at 70 mph. It provides the sound enthusiasts want without being overly punishing for daily use.

Installation

This was the easiest installation by a wide margin. With just two 14mm bolts per side, you reuse the OEM hangers for a perfect fit. This is a genuine 15-minute driveway job that requires no lift or specialized tools.

Build Notes

The use of premium 304 stainless steel ensures excellent resistance to corrosion, even in regions with heavy road salt. The CNC-machined ⅜” flanges and clean TIG welds inspire confidence in the system’s long-term durability.

• Pros: Fastest install and lightest weight (-11 lbs); highest dyno gain; premium 304 stainless.
• Cons: Specific to the VB-chassis only; volume may be too spirited for commuters who prefer a quiet ride.

Best For: 2022+ WRX owners chasing quick, meaningful gains without visiting an exhaust shop.

Value Verdict: “The perfect first mod—power you can feel, sound you can brag about, and an install you can do on your lunch break.”

Key Insight: The WRX system is the clear performance winner, delivering the highest power gains (+9hp), the fastest install (15 min), and premium 304 stainless steel construction.

Side-by-Side Comparison

Feature	Camry	Q50	WRX VB
Material	16-g SS	16-g SS	304 SS
Install Time	1–2 h	1–1.5 h	15 min
HP / TQ Gain	+5 / +4	+6 / +4	+9 / +8
Weight Saving	-8 lb	-7 lb	-11 lb
Sound Level (10=Wild)	7	6	8
AWD Compatible	No	Yes	Yes
Warranty	1 year	1 year	1 year

Overall Winners & Final Verdict

After thorough testing, it’s clear that the “best” exhaust depends entirely on your vehicle and goals. All three systems delivered on their promise of quality construction and proven gains. However, each excelled in a different area.

• Best Overall Performance: The Subaru WRX VB system takes the crown with the highest horsepower and torque delta.
• Best Value: The Infiniti Q50 unit offers an unbeatable combination of low cost, AWD compatibility, and refined sound.
• Best Sound: For transforming a car’s character, the Toyota Camry system is the winner with its aggressive quad-tip bark.
• Most Daily-Driver Friendly: The Infiniti Q50 stands out again for having the quietest cabin presence and an OEM-like fit.

The bottom line is that each of these axle-backs is a well-engineered product. Your specific platform and priorities, whether performance, sound, or value, will dictate the right choice for you.

How to Choose Your Axle-Back

Still not sure which is right for you? Here’s a simple decision guide to help you select the best option based on your car and preferences.

Choose the Camry unit if you…

• Drive a 2018-2024 FWD Camry and crave an assertive exhaust note.
• Don’t mind trimming the lower diffuser a tiny amount for the perfect fit.
• Want aggressive quad-tip aesthetics at an affordable price.

Choose the Q50 unit if you…

• Own a 2014-2020 Infiniti Q50 (RWD or AWD).
• Prefer a subtle, sporty sound with minimal impact on cabin quietness.
• Seek the lowest-cost entry point for performance mods.

Choose the WRX VB unit if you…

• Pilot a 2022+ Subaru WRX and want noticeable gains in turbo response.
• Value the long-term durability of 304 stainless steel.
• Appreciate a true driveway installation that’s faster than ordering take-out.

Installation Guide Summary

All three systems are designed for DIY installation. Here are the general steps:

1. Safely raise the rear of the car on jack stands or ramps and allow the exhaust to cool completely.
2. Spray penetrating oil on the axle-back flange bolts and let it soak in.
3. Unbolt the factory muffler section and carefully slide it off the rubber exhaust hangers.
4. Position the new exhaust, slide the rods into the hangers, and loosely thread the new hardware.
5. Align the tips so they are centered and flush with the bumper, then torque the bolts to spec.
6. Start the engine, check for any leaks at the flange, and re-torque the bolts after the first 50 miles.

Vehicle-Specific Notes: The Camry may require a ¼” trim on the diffuser lip. For the Q50, ensure the mid-pipe gasket stays centered. The WRX has no special notes, as it’s the easiest fit of the three.

Tools Required: You will need a 14mm deep socket, a 3/8″ ratchet, a breaker bar for stubborn bolts, a torque wrench, and exhaust hanger pliers.

Pro Tip: After your first 50 miles, re-torque the flange bolts. Heat cycles can cause initial loosening, and this simple step ensures a permanent, leak-free seal for your new exhaust.

Performance Expectations & Real-World Gains

While some argue that axle-back systems are mainly about noise and looks, our tests show they offer real gains by modifying the heaviest mufflers. Others suggest they have minimal performance impact, but you can realistically expect a 2-4% horsepower increase on naturally aspirated engines and a 3-4% increase on turbocharged motors.

These gains are foundational and will stack with future mods like high-flow downpipes or an ECU tune. The most immediate change is the sound improvement, which is typically a 5–10 dB increase. No tune is required, as these systems retain all factory emissions equipment, adding sound and small power gains legally.

Key Insight: An axle-back is a ‘no-tune-required’ mod. It provides a foundational 2-4% power bump and a major sound upgrade while remaining fully emissions-legal, making it a safe first choice.

Quality & Durability Assessment

The materials and construction methods used are critical for longevity. The Camry and Q50 systems use corrosion-resistant 16-gauge stainless steel. The WRX unit steps up to marine-grade 304 stainless for maximum durability.

The use of TIG welding on all three systems results in stronger, cleaner beads compared to more common MIG welding. Furthermore, mandrel bends ensure the pipe diameter remains consistent through curves. With occasional cleaning, these systems should last 5–10 years and are backed by a 1-year warranty.

Real-World Driving Impressions

On the road, each system revealed its unique character.

• Highway: The Q50 was impressively hushed at 70 mph, making it the best long-distance companion. The WRX transmitted a purposeful rumble, while the Camry sat neatly between the two in cabin volume.
• Spirited Driving: All three systems sharpened throttle response, with the WRX feeling especially eager coming out of corners.
• City: Idle volume is only modestly increased across the board, so none of the systems will trigger unwanted glares from neighbors.
• Cold Start: The WRX barks the loudest on a cold start before quickly settling into a deep idle, while the Q50 remains the most civically polite.

Frequently Asked Questions

Q: Do I need a tune after installing an axle-back?

A: No. These systems are installed after the catalytic converters, and the factory ECU can easily adapt to the change in airflow. No tune is required.

Q: Will this void my vehicle’s warranty?

A: Federal law prohibits a manufacturer from voiding your entire warranty for using an aftermarket part. It’s always a good practice to keep your original parts just in case.

Q: Are these systems legal for emissions?

A: Yes. Since no catalytic converters or other emissions-control devices are removed or altered, these systems are emissions-legal.

Q: Is there any highway drone?

A: Drone is minimal on the Q50. The Camry and WRX have a moderate but manageable presence, which is typical for more aggressive systems.

Disclosure & Transparency

For this review, we purchased the Camry and WRX systems directly. The Q50 unit was supplied on loan by the manufacturer for testing and was returned after the review was completed.

All dynamometer sessions were conducted under identical, controlled conditions to ensure fair and accurate results. Our opinions, data, and conclusions remain our own.

Your Next Steps

Choosing the right exhaust comes down to understanding your vehicle and performance goals. Whether you prioritize raw power for your WRX or a refined tone for your Q50, a quality axle-back is a rewarding first mod.

Pick your platform, grab the right system, and enjoy the new sound and response. Questions? Drop them in the comments below, and we’ll help you choose, install, and enjoy your new exhaust.

Author Profile: Private Label Mfg (PLM) is the leading manufacturer of high-performance aftermarket automotive parts for Honda, Subaru, and other popular JDM and European vehicles.