BMW X3M / X4M Stage 1 & Stage 2 ECU Remapping

The BMW X3M and X4M combine SUV practicality with supercar-level performance, thanks to the incredible S58 twin-turbo engine. At our Slough-based performance tuning workshop, we unlock their full potential with custom Stage 1 and Stage 2 ECU remapping, delivering sharper throttle response, increased power, and even more exhilarating acceleration.

Our Stage 1 ECU remap is the perfect choice for standard vehicles. By optimising boost pressure, fuel delivery, and ignition timing, we safely extract significant gains in both horsepower and torque – all while retaining the factory reliability and smoothness that makes these M models such versatile daily drivers.

For those looking to push performance even further, our Stage 2 tuning combines our advanced ECU software with carefully matched hardware upgrades such as a high-flow downpipe, uprated intercooler, and performance intake. This setup improves airflow and cooling efficiency, allowing us to maximise the S58’s potential for consistent, track-ready performance without sacrificing drivability.

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Why Choose Onyx Performance?

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We’ve been proudly featured on Carwow – a testament to the quality, professionalism, and performance-focused results that set us apart. Watch our feature here to see us in action.

Expertise You Can Trust

With years of experience and deep technical knowledge, our team understands performance vehicles inside and out – from custom remaps to high-end servicing.

Advanced Workshop & Tools

We operate from a state-of-the-art facility in Slough, equipped with cutting-edge diagnostics, dyno testing, and industry-leading tools for accurate, high-quality work.

Tailored Solutions for Every Vehicle

We don’t believe in one-size-fits-all. Every car gets a bespoke approach, ensuring the best results whether it’s a remap, upgrade, or routine service.

Trusted Nationwide

Performance enthusiasts from across the UK come to Onyx because they know they’ll receive premium-quality workmanship, careful attention to detail, and honest advice.

Complete Care, All in One Place

From tuning and servicing to tyres, trackers, and immobilisers – we offer a full suite of services under one roof, all with a strong focus on safety, reliability, and top-tier customer support.

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Book Your BMW X3M / X4M Stage 1 or Stage 2 Remap in Slough

Experience the ultimate transformation with our BMW X3M and X4M custom ECU remapping. Whether you choose Stage 1 for a safe, instant boost or Stage 2 for peak performance with supporting hardware, our Slough tuning specialists deliver precision, reliability, and breathtaking results. Book now and unleash your S58’s full power.

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Why Choose Onyx Performance for Servicing?

Experts in Performance Cars

We know how to properly care for performance, modified, and luxury vehicles. Our team has the skills and experience to handle specialist requirements confidently.

Correct Service Schedules

Every service follows the exact schedule recommended by your vehicle’s manufacturer, helping maintain performance and protect your warranty.

Quality or OEM Parts

We only use high-quality aftermarket or original manufacturer parts, ensuring long-lasting reliability and top-level performance.

Full Vehicle Inspection

Our service goes beyond just changing oil. We inspect all key systems to keep your car safe, smooth, and road-ready.

Honest Advice, No Surprises

With transparent pricing and expert recommendations, you’ll always know what your car needs – no upselling, no hidden fees.

Fast, Trusted & Tracked

We offer quick turnaround, maintain service records, and send reminders – that’s why customers travel to us from across the UK.

Frequently Asked Questions

What gains can I expect from Stage 1?

Stage 1 typically delivers 60–90 bhp and a strong increase in torque across the rev range.

Is Stage 1 suitable for a completely stock car?

Yes – it’s designed to work perfectly with the standard engine and exhaust setup.

What extra hardware is required for Stage 2?

Stage 2 requires a sports downpipe, upgraded intercooler, and performance intake for maximum results.

Will this affect my car’s drivability?

No – both stages are tuned for smooth power delivery, making them ideal for daily use.

Do you offer dyno testing for the X3M/X4M?

Yes – we provide before and after dyno runs so you can see the exact performance gains.

Can Stage 2 tuning be used on track?

Absolutely – our Stage 2 maps are engineered for sustained high-performance driving, including track use.

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