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Cat Back Exhaust

This part does not affect the base vehicle warranty.

mountune has many years of experience in engineering exhaust systems with the objective of increased power and response, coupled with an enhanced exhaust tone and appearance.

The mountune Performance mk3 Focus ST cat back exhaust system is manufactured from 2.5” diameter, AISI 304 stainless steel (EN58E) mandrel-bent tubing with lazer cut flanges. All muffler assemblies are robotically TIG welded AISI 304 stainless steel for long life under extreme performance and feature consistent internal diameter throughout the entire length of the assembly.

To ensure improved performance while controlling sound, each muffler includes a three-layer hybrid synthetic sound absorption packing that eliminates droning, booming, and other undesirable tones. Tubing diameter also has a major impact on sound quality and careful consideration was given to size and performance.

Also incorporated are slip-fit connections at various strategic points to allow for easy installation and adjustment.

Crucially, the mountune cat-back exhaust is the only exhaust system that will not affect your base vehicle warranty and in addition, comes with a mountune limited lifetime warranty*.


  • Manufactured from AISI 304 2.5” mandrel bent stainless steel tubing
  • TIG welded construction AISI 304 stainless steel hangers
  • Mufflers feature consistent internal diameter 3-layer hybrid synthetic muffler packing effective to 900 degrees C
  • Large 4” rolled edge, polished stainless steel tips with mountune logo
  • Full width rear hanger ensures stable tip location
  • Heavy duty "boss" type clamps
  • CAD engineered and designed
  • Limited lifetime warranty*
  • Does not affect Ford vehicle warranty

Recommended to fit in conjunction with mk3 Focus ST Sports Cat / Downpipe.

Please note: Not compatible with Wagon models. See wagon specific product here.

*Please contact us for warranty terms and conditions.

    Customer Reviews
    4.8 Based on 59 Reviews
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    Filter Reviews:
      ERIC A.
      United States United States
      Perfect exhaust for me and Mountune delivered!

      My 2017 ST has had the stock exhaust for a while now. I didn’t want something too loud so I kept it stock. After reading reviews and watching exhaust videos, I chose the Mountune. I tried buying this exhaust from a U.S. dealer but for some reason nobody stocks it. I was surprised to see that Mountune U.K. had it in stock and could ship it to California. Got the unit in 5 days! Not going to lie. The pipe that goes over the rear axle was real pain but I managed. Did the whole job solo and took it for a spin afterwards. My first destination was a tunnel by the local airport. It made that sound that I have missed since my old car. Props to Mountune for making this stay at home time a little more enjoyable.

      United Kingdom United Kingdom
      Nice system

      Ordered my system from Mountune. Ordered it lunchtime on the Wednesday came lunchtime on the Thursday, was very happy with that. Got it all fitted today 08/03/2020. Was fairly straightforward if you follow the pics from the website. The over axle piece can be tricky to fit, but eventually went in. Once it was on, the system isn't too loud, is great for everyday use. One bit to go and I am looking for the MR300 map :) super happy!!!

      United Kingdom United Kingdom
      cat back exhaust

      service was excellent top quality exhaust the sound is spot on not loud just right no drone at all I have a smile every time I put my foot down a big thanks to mountune