Milltek's Active Valved Cat-Back for the Ford Mustang Shelby GT500 (S550, 2020 to 2023) is a valve-controlled 2.76-inch (70mm) T304L stainless steel exhaust that switches between a refined cruise and a full supercharged roar, at direct OEM fitment. It is built for GT500 owners who want the 5.2 V8 to sound as serious as it drives, without committing to one fixed volume. It bolts to the factory hangers and mounting points, so fitting needs no cutting or welding.
What is the Milltek valved cat-back for the GT500?
It is a full cat-back replacement, every section from the catalytic converters rearward, built in hand-finished T304Lstainless and mandrel-bent 2.76-inch (70mm) pipe. Vacuum-actuated valves open and close the exhaust path, so the same system gives a quieter, drone-controlled tone with the valves shut and the full supercharged V8 volume when they open. You control it through the car's drive modes or a switch.
Who is it for?
It suits the GT500 owner who drives on road and track and wants both civility and drama from one system. If you want a single fixed volume at a lower price, a non-valved cat-back is simpler. The valved system keeps the peace on a cold start or a late drive home, then opens up on demand.
What does it include and what are the specs?
The system ships as a complete valved cat-back with your chosen tip finish, OEM-compatible hangers and the fixings for a bolt-on fit.
| Material |
T304Lstainless, hand-finished |
| Pipe diameter |
2.76" (70mm), mandrel-bent |
| Configuration |
Valved cat-back (driver-selectable, vacuum-actuated) |
| Tip finishes |
Polished, Brushed Titanium, Burnt Titanium, Cerakote Black |
| Fitment |
Ford Mustang Shelby GT500 5.2 V8 Supercharged (S550) 2020 to 2023 |
| Install |
Direct OEM fitment, no cutting or welding |
What are the limitations, and who is it NOT for?
This is a cat-back, so it does not replace the catalytic converters or headers. It is a sound, flow and weight upgrade, not a power conversion, and on a cat-back alone expect a modest power change rather than a headline dyno figure. If you want the loudest possible system at all times, a fixed non-valved exhaust is simpler and cheaper.
Every system is built in hand-finished T304L stainless. (Source: Milltek Sport, About Us.)
Last updated: 2026-07-01.
Designed in Tennessee and manufactured in the UK with 40+ years of performance exhaust heritage. Tested on the Tail of the Dragon.
Vehicle fitment
- 2020-2023 Ford Mustang Shelby GT500
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