Price really hinges on condition, mileage, trim (think V6, GT, Shelby, or Roush), and any mods. A clean Roush Stage 3 with low miles can easily push past $15k, whereas a beat‑up high‑mileage V6 might hover around $2.5k.
A 2006 Roush Mustang makes 300 hp in Stage 1 and Stage 2, and 415 hp in the supercharged Stage 3
Stage 1 and Roush Stage 2 start with the stock 4.6L V8, then Roush adds an intake, exhaust, and some tuning tweaks. Stage 3 goes further, bolting on a Roots‑type supercharger and beefing up the internals. Those numbers come straight from Roush’s 2006 spec sheets, which also note that the base GT puts out about 300 hp. If you want the exact figure for a particular car, look at its dyno or build sheet—aftermarket tweaks can nudge a Stage 3 up to 450‑475 hp.
Source: Edmunds
What is the Roush package?
The Roush package is a performance and cosmetic upgrade program that offers Stages 1‑3 for Ford vehicles, primarily Mustangs and F‑150s
The Roush package is a performance and cosmetic upgrade program that offers Stages 1‑3 for Ford vehicles, primarily Mustangs and F‑150s
Each step adds more power, handling tweaks, and visual upgrades like body kits, badges, suspension tweaks, and interior trim. Roush builds these packages at its Michigan plant or through authorized dealers, usually backing them with a limited warranty. The result is a turnkey ride that blends show‑ready looks with track‑capable performance.
Source: MotorTrend
A 2005 Roush Stage 1 Mustang was a cosmetic‑only package that left the engine, transmission, and suspension unchanged
It added Roush‑specific badging, graphics, a deck‑lid emblem, windshield banner, embroidered floor mats, and a full body kit (front fascia, side skirts, rear valance). The powertrain stayed the stock 300 hp 4.6L V8 paired with either the 4R100 automatic or Tremec manual. Owners picked Stage 1 for the Roush look and brand prestige without paying for power upgrades.
Source: Edmunds
Are Roush exhausts legal?
Most street‑legal Roush exhaust systems for the 2006 Mustang are designed to meet federal and state emissions and noise standards
Roush engineers its street exhausts to keep the factory catalytic converters and mufflers, so they stay compliant with OEM emissions rules and local noise limits (usually under 80‑85 dB). They also offer “Track” or “Competition” versions that ditch emissions gear and exceed street‑legal noise—those are strictly for closed‑course use. Always check for a CARB exemption or 50‑state legality label before you bolt one on.
Source: NHTSA
Source: EPA
Are Roush axle backs street legal?
Because axle‑backs only swap out the mufflers and tailpipes behind the rear axle, they don’t touch emissions equipment, so they usually pass state inspections even in strict places like California. The main issue is noise: louder axle‑back setups (like the “Track” mode) can break residential noise ordinances and draw complaints. Testing the sound on public roads before final installation helps you avoid tickets.
Source: EPA
Are axle backs legal?
Axle‑back exhaust systems are legal when they retain the factory catalytic converters and comply with applicable noise regulations
Since they don’t mess with the emissions‑control hardware, axle‑backs typically meet federal emissions standards; the only variable left is sound output. Many towns enforce decibel limits for vehicle exhaust, especially at night, so picking a muffler with a moderate tone helps you stay legal. Always verify your state’s inspection rules and local noise ordinances before installing an axle‑back.
Source: EPA
Are Catback exhausts loud?
Catback exhaust systems are louder than stock, but the increase in volume varies by design and usually ranges from 5 to 10 dB
A catback replaces the exhaust piping from the catalytic converter rearward, often using larger‑diameter tubing and less restrictive mufflers, which cuts backpressure and raises the exhaust note. The exact loudness depends on muffler construction, whether a resonator is present, and pipe size—some “touring” catbacks aim for a subtle growl, while “race” versions can be pretty aggressive. Grabbing a decibel meter at idle and under load gives you a concrete sense of the change.
Source: Car and Driver
Are Catback exhausts illegal?
A catback exhaust is not illegal by itself if it retains the catalytic converter and meets local noise limits
Illegality only shows up when the catback removes or bypasses the catalytic converter, which violates federal emissions laws enforced by the EPA. Many aftermarket catbacks are sold as “50‑state legal” or CARB‑exempt precisely because they keep the cat intact. Even with a legal catback, excessive noise can still trigger citations under local ordinances, so you need to verify both emissions compliance and sound levels.
Source: EPA
Is a Catback louder than a muffler delete?
A muffler delete is generally louder than a catback exhaust because it removes the muffler entirely, while a catback retains some muffling
Yanking the muffler cuts out a major source of sound attenuation, often boosting the exhaust note by 10‑15 dB or more versus a stock system. A catback, even with a performance muffler, still has some absorption and reflection chambers that temper the volume. So a muffler delete gives a sharper, more aggressive tone, whereas a catback delivers a noticeable increase over stock but usually less sheer volume than a straight‑through delete.
Source: MotorTrend
Does muffler delete increase HP?
A muffler delete typically yields only a modest horsepower gain, often in the range of 5‑10 hp
The benefit comes from reduced backpressure, which lets the engine expel exhaust gases a tad more freely, but the effect is small because the muffler is just one restriction in the exhaust stream. Most of the perceived performance bump is auditory rather than real power. For meaningful gains, you’d want to tackle the whole exhaust system (headers, high‑flow cats, catback) or dive into engine tuning.
Source: Edmunds
Is Catback louder than straight pipe?
A straight‑pipe exhaust (no muffler, no catalytic converter) is louder than a catback, which retains at least some muffling and the catalytic converter
Straight‑pipe setups strip out all sound‑deadening parts, churning out a raw, high‑volume exhaust note that can top 100 dB under acceleration. A catback, even with a performance muffler, still has some absorption chambers and keeps the catalytic converter, which together dampen the sound compared to a fully open pipe. So while a catback is noticeably louder than stock, it stays quieter than a true straight‑pipe configuration.
Source: MotorTrend
Does a muffler delete Make your car faster?
A muffler delete does not make a car significantly faster; any speed improvement is negligible
The slight reduction in backpressure might add a few horsepower, but the impact on acceleration times usually falls within the margin of error of a typical dyno test. In some cases, losing backpressure can actually hurt low‑end torque, making the car feel slower off the line. Real‑world performance gains need a broader approach—intake, exhaust headers, tuning, and possibly forced induction.
Source: Edmunds
Are straight pipes bad for your engine?
Straight‑pipe exhausts are not inherently destructive, but they can cause tuning issues, excessive noise, and accelerated wear if the engine is not re‑calibrated
Pulling the muffler and catalytic converter lowers backpressure, which may call for tweaks to fuel mapping or ignition timing to keep combustion optimal. Without those adjustments, the engine can run leaner at certain RPMs, potentially raising exhaust‑gas temperatures and stressing valves over time. Plus, the increased cabin noise and drone can lead to driver fatigue and might violate local noise ordinances, resulting in fines.
Source: MotorTrend
