Ford Focus ST Mk4 Performance Parts & Tuning Mods

Top Brands For Ford Focus ST Mk4

The Ford Focus ST Mk4 is well supported by leading performance parts manufacturers, so you will find a strong range of trusted brands for tuning, styling and motorsport upgrades. Explore popular names known for reliable power, handling and braking mods below.

Ford Focus ST Mk4 Exterior Styling Upgrades

You can really sharpen the look of your Ford Focus ST Mk4 with a mix of exterior styling mods, from full body kits and aggressive splitters to spoilers, diffusers, custom grilles and more. Whether you want a cleaner OEM+ vibe or a track-ready stance, there are upgrades to make your ST stand out.

Suspension & Handling Upgrades

The Focus ST Mk4 is sharp out of the box, but a few key mods really wake up its agility. Start with tyres and brakes, as good rubber and uprated pads transform confidence. A quality performance tyre gives more bite on turn in and better traction out of tight bends, while performance brake pads, grooved discs and braided lines give stronger, more consistent stopping on fast road or track days without feeling grabby. From there, look at suspension tuning. The factory setup can feel a touch soft and prone to understeer when you push on, so lowering springs or a well matched coilover kit will tighten body control and reduce roll without ruining ride quality if you choose sensibly. Upgraded dampers, thicker anti roll bars and a rear strut brace help the Ford Focus ST Mk4 feel more planted and adjustable mid corner. Fresh performance bushes sharpen steering response, so the car feels more precise and playful on B roads and circuits alike.

Frequently Asked Questions about Ford Focus ST Mk4 Upgrades

What are the best first performance mods for a Ford Focus ST Mk4?

The usual first upgrades on a Focus ST Mk4 are an ECU remap, a high flow panel filter or intake kit, and a cat back exhaust system. Together they help the 2.3 EcoBoost breathe better and make the most of the factory turbo without going too wild.

A decent remap alone can give a noticeable bump in horsepower and torque, sharper throttle response and stronger mid range pull. Adding an intake and freer flowing exhaust helps keep intake temps and back pressure under control so the engine can repeat that performance consistently.

If you plan to push harder later, it is also worth fitting uprated spark plugs and fresh, good quality oil early on, as cheap preventative maintenance to support the extra power.

Is a remap safe for my Focus ST Mk4 and will it affect reliability?

A well written, stage 1 ECU remap for the Focus ST Mk4 that is designed for a standard car and run on good quality fuel is generally considered safe. The stock internals and turbo can handle a sensible increase in boost and torque for fast road use.

Reliability comes down to how the car is driven and maintained. Warm it up properly, use decent oil, stick to regular servicing and avoid constant high boost abuse when hot, and the engine should cope fine with mild to moderate tuning.

Poor maps, low octane fuel and ignoring basic checks are what tend to cause issues. At Progressive Parts we always recommend using reputable software and pairing it with supporting mods like an intercooler and intake once you start pushing beyond a simple stage 1 tune.

Will tuning my Ford Focus ST Mk4 void the warranty or affect insurance?

Any performance tuning or ECU remap can affect your manufacturer warranty. Ford could refuse a warranty claim if they believe a modification contributed to the failure. Even simple bolt ons like exhausts or intakes can raise questions if a related component fails.

Insurance wise, you must declare all mods, including remaps, exhausts, wheels and suspension upgrades. Some insurers are very mod friendly, others are not, but failing to declare your upgrades can invalidate your cover if you ever need to make a claim.

If your car is still under manufacturer warranty, it is worth speaking to your dealer and insurer before you start modifying, so you know exactly where you stand.

What supporting mods do I need for a stage 2 or more aggressive tune?

Once you move beyond a basic stage 1 remap on the Focus ST Mk4, you will want to look at supporting hardware. A larger or more efficient front mount intercooler, an upgraded intake system and a high flow sports cat or de cat downpipe are usually the next steps.

The intercooler helps control intake air temps when running more boost, which keeps power repeatable and protects the engine. A freer flowing downpipe and exhaust reduce back pressure and turbo stress, helping the turbo spool more cleanly.

At this level it is also wise to consider uprated clutch components on high mileage cars, better tyres and possibly suspension and brake upgrades, so the chassis can handle the extra speed safely.

What wheel and tyre sizes work well on a Focus ST Mk4 for fast road use?

The Focus ST Mk4 comes with sporty alloys from the factory, but many owners upgrade to aftermarket wheels or rims for better grip, looks and fitment around big brake kits. A common fast road setup is 18 or 19 inch wheels with a slightly wider performance tyre.

Sticking close to the stock rolling radius keeps the handling balance and speedo accuracy sensible. For example, moving to a wider tyre on a suitable offset wheel can improve traction without causing rubbing if the car is lowered moderately on springs or coilovers.

If you are planning aggressive lowering or track use, it is best to check offset, width and tyre choice carefully, and be prepared to add alignment tweaks like a bit more negative camber to keep everything clearing the arches under load.

How much power can I reasonably expect from basic bolt on mods and a remap?

On a healthy Focus ST Mk4, a good quality stage 1 remap on an otherwise standard car can usually deliver a noticeable gain in torque across the rev range, with a modest but clear increase in peak horsepower. The car will feel stronger in the mid range and more responsive.

Adding a performance intake, intercooler and freer flowing exhaust, then moving to a stage 2 style tune, can build on that with further sensible gains. You will feel the difference in how the car pulls through the gears, especially on a spirited B road drive.

Exact numbers depend on fuel quality, dyno type and the particular map, so it is better to think in terms of a stronger, more usable powerband rather than chasing headline figures.

Do I need to upgrade the brakes and suspension when tuning my Focus ST Mk4?

The standard Focus ST Mk4 brakes and suspension are decent for road use, but once you start increasing power and driving harder, supporting chassis mods make a big difference to confidence and safety.

Simple upgrades like performance brake pads, quality discs and fresh fluid improve stopping power and fade resistance. A set of lowering springs or coilovers, combined with uprated anti roll bars or bushings, can tighten up the handling without making the car unusable day to day.

You do not have to do everything at once, but planning brake and suspension upgrades alongside your power mods keeps the whole package balanced and enjoyable to drive.

Is a full exhaust system worth it on a daily driven Ford Focus ST Mk4?

A quality cat back exhaust on the Focus ST Mk4 offers a small performance benefit by reducing back pressure, but the main gains are response, sound and longevity. You get a sharper throttle feel, a sportier tone and usually a weight saving compared to the stock system.

For a daily driver, look for an exhaust with a resonated option so you avoid excessive drone on the motorway. Pairing the cat back with a sports cat or high flow downpipe can unlock further performance with the right remap, while still being usable and civil on the road.

As always, choose reputable brands and check local MOT and emissions rules if you are considering more aggressive options like a de cat pipe for track use.

Ford Focus ST Mk4 Final Thoughts

The Ford Focus ST Mk4 is a cracking all round hot hatch, with strong out of the box performance, a punchy turbo engine and a practical cabin that still feels special on the right road. It has the right foundations for serious tuning, which is why so many owners look to maps, exhaust systems and intake kits to unlock a bit more character and usable power. With sensible performance parts and quality software, you can see noticeable gains without turning the car into something awkward to live with every day. From the factory the Focus ST Mk4 can suffer with heat management on hard use, especially once you start increasing boost and power. An upgraded intercooler, intake and exhaust system helps keep intake temps under control, lets the turbo breathe and adds a more involving soundtrack without going over the top. The stock clutch and drivetrain are generally fine at standard levels, but once torque climbs, many enthusiasts move to stronger clutches and mounts to cope with spirited driving and track days. On the chassis side, the standard suspension is comfortable but a little soft and prone to roll when pushed, and the factory wheels and tyres can hold the car back on road and circuit. Coilovers or matched springs and dampers, uprated anti roll bars and better tyres transform turn in and grip, while big brake kits or performance pads and discs give you the confidence to brake later and harder. Subtle styling tweaks, from lighter alloys to aero parts and interior upgrades, finish things off and make your Focus ST look as sharp as it goes. Put together in the right way, these mods turn the Ford Focus ST Mk4 into a properly sorted performance hatch that still copes with commuting, shopping runs and family duties. The key is balancing power, handling and reliability, using proven tuning packages and motorsport grade components rather than chasing numbers. Build it around how you drive, and you will end up with a fast, reliable and genuinely rewarding Focus ST that feels uniquely yours every time you get behind the wheel.