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 (S650 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 or resonated versions, 5 tailpipe finishes and a choice of outlet (Dual, Quad), 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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EC Approved: No
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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 4 tailpipe finishes: GT-100 Brushed Titanium, GT-100 Burnt Titanium, GT-100 Cerakote Black, GT-100 Polished
- 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: Dual Quad Outlet with Active Valves Non-Resonated with GT-100 Brushed Titanium Trims - Requires OE GT 5.0 Rear Diffuser. Some versions: Dual Quad Outlet with Active Valves Non-Resonated with GT-100 Burnt/Blue Titanium Trims - Requires OE GT 5.0 Rear Diffuser. Some versions: Dual Quad Outlet with Active Valves Non-Resonated with GT-100 Cerakote Black Trims - Requires OE GT 5.0 Rear Diffuser. Some versions: Dual Quad Outlet with Active Valves Non-Resonated with GT-100 Polished Trims - Requires OE GT 5.0 Rear Diffuser. 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 Brushed Titanium, GT-100 Burnt Titanium, GT-100 Cerakote Black, GT-100 Polished. 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?
Milltek does not list EC approval for this part. Any exhaust used on the road must still meet noise and emissions rules, so check the requirements where you live.
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.
