Milltek Cat-back Exhaust for Ford Mustang 2.3 EcoBoost (S550 Fastback) (2015-2018) – Sharper Sound, Reduced Back Pressure
This is Milltek's cat-back system for the Ford Mustang 2.3 EcoBoost (S550 Fastback). It replaces everything from the factory catalytic converter rearward with wider-bore pipework, a re-profiled mid-pipe and silencers tuned specifically for this platform, cutting back pressure and sharpening the exhaust note. The factory catalytic converter stays in place, so the car's emissions hardware is left as standard. It's offered in non-resonated, resonated EC approved or resonated versions and 7 tailpipe finishes, so you can pick the setup that suits how the car's used.
It's aimed at owners who want a noticeably different sound and a genuine, if modest, flow improvement without touching anything upstream of the cat: a straightforward bolt-on that doesn't need a remap or any other supporting mods to enjoy.
Specifications
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System Type: Cat-back
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Pipe Diameter: 70mm (2.76")
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Race System: No
Key Features
- Made from T304L aircraft-grade stainless steel, which is anti-magnetic and resists discolouration
- Mandrel-bent pipework keeps a constant diameter through every bend for unrestricted flow
- 70mm (2.76") pipework
- Replaces the standard exhaust from the catalytic converter back, so the factory cat is retained
- Choice of 7 tailpipe finishes: GT-100 Burnt Titanium, GT-100 Cerakote Black, GT-100 Polished, GT-100 Titanium, GT-90 Cerakote Black, GT-90 Polished, GT-90 Titanium
- EC approved versions available
- Resonated (quieter) or non-resonated (louder) versions
- Designed, developed and manufactured in the UK by Milltek Sport
Fitment
- Ford Mustang 2.3 EcoBoost (S550 Fastback) (2015-2018)
- Ford Mustang 2.3 EcoBoost (S650 Fastback) (2024 onwards)
Not every version fits every car in this list. Check the fitment shown for the option you select.
Not suitable for: any model, engine or body style not listed above. Check your car before ordering.
Installation
Some versions: Quad Outlet Non Resonated with GT-90 Cerakote Black Trims (requires Roush Performance Rear Valance). Some versions: Quad Outlet Non Resonated with GT-90 Polished Trims (requires Roush Performance Rear Valance). Some versions: Quad Outlet Non Resonated with GT-90 Titanium Trims (requires Roush Performance Rear Valance). Some versions: Quad Outlet Resonated with GT-90 Cerakote BlackTrims (requires Roush Performance Rear Valance). We recommend professional fitting on a ramp. Once fitted, check the tailpipe alignment and re-check all clamps after the first few hundred miles.
Upgrade Further
Also available from Milltek for this car: Milltek Downpipe & De-cat Ford Mustang 2.3 EcoBoost S550 Fastback 15-18.
What's the difference between the resonated and non-resonated versions?
The resonated version adds extra silencing for a quieter, more refined tone. The non-resonated version leaves it out, so it is louder and more aggressive.
Which tailpipe finishes are available?
You can choose from: GT-100 Burnt Titanium, GT-100 Cerakote Black, GT-100 Polished, GT-100 Titanium, GT-90 Cerakote Black, GT-90 Polished, GT-90 Titanium. The finish is cosmetic and does not change the sound.
Will it fit the Ford Mustang 2.3 EcoBoost (S650 Fastback)?
Yes. Milltek lists this part for the Ford Mustang 2.3 EcoBoost (S650 Fastback) as well as the other models in the fitment list above.
Is it road legal?
Some versions are EC approved; check the EC Approved line in the specification for the option you choose.
Do I need a remap?
No. It fits behind the factory catalytic converter, so no software changes are needed.
Does it keep the factory catalytic converter?
Yes. It fits behind the factory catalytic converter, which stays in place.
What is it made from?
T304L aircraft-grade stainless steel, which is anti-magnetic and resists discolouration better than lower grades.
Is there a warranty?
Yes. Milltek products are covered against defects in materials and workmanship. Contact us with your order number if you have a problem.
