Ford Focus ST2 2005

Service Completed: Ford Focus ST 2005 2.5L Petrol Custom 3-Inch Cat-Back Exhaust System

At MIJ Exhaust Ltd, we recently completed a full custom 3-inch big bore cat-back exhaust system on this Ford Focus ST 2.5L Petrol, delivering improved exhaust flow, a more aggressive sound, and a striking new rear-end finish.

For this build, we fabricated a complete mandrel-bent 3-inch cat-back system, replacing the restrictive factory exhaust with a larger diameter setup designed to maximise performance and efficiency. Mandrel bending ensures the pipe maintains a consistent internal diameter through every bend, allowing exhaust gases to flow more freely compared to conventional bent pipework.

The benefits of a 3-inch big bore system include improved exhaust flow, reduced back pressure, a deeper and more responsive exhaust note, and the potential to support increased power on both standard and modified vehicles. It’s an ideal upgrade for Focus ST owners looking to unlock more of the five-cylinder engine’s character while future-proofing the car for additional performance modifications.

One thing that sets a truly custom exhaust apart is the ability to build it specifically for the vehicle rather than making a universal system fit. Not every car has a perfectly straight exhaust route, and this Focus ST is a great example. As you’ll see in the images, the exhaust follows the contours of the vehicle’s underside, running level before gradually dropping towards the rear. It’s not an over-axle or under-axle design—it’s simply the shape of the vehicle, and the exhaust has to be fabricated to suit it perfectly.

This is where experience makes all the difference. Every section of the system was carefully measured, fabricated, and welded in-house to follow the vehicle’s natural contours while maintaining excellent ground clearance, correct clearances from surrounding components, and a factory-quality fit.

To complete the build, we finished the system with a pair of premium double-skinned 4-inch slash-cut chrome exhaust tips, giving the rear of the Focus ST a bold, high-performance appearance that perfectly complements the custom exhaust.

As with all of our work, this system was handcrafted in-house using high-quality materials and precision fabrication techniques to ensure exceptional durability, fitment, and finish.

We’ve also captured the build process and the final sound test, so be sure to check out the video below to see how the system was made and hear the unmistakable tone of the Focus ST’s iconic 2.5L five-cylinder engine.
https://www.instagram.com/p/DZb73FylLoR/

Why Choose a Custom MIJ Exhaust?

No two vehicles—and no two customers—are alike. That’s why every exhaust system we build is custom-made on the vehicle for the perfect fit, tone, and performance.

Whether you’re after:

A sportier, more aggressive sound,

A performance-focused setup, or

A refined, OEM-style tone,

—we tailor the design specifically to your goals.

More Than Just Custom Builds

We provide all types of exhaust services, including:

Exhaust repairs and leak fixes

Section replacements

Welding cracks and fault correction

Tailpipe upgrades and cosmetic enhancements

Small adjustments and one-off jobs