X4 M40i (G02)

Most mechanical parts are shared. The G01 X3 M40i and G02 X4 M40i use the same B58 engine, gearbox, brakes and much of the suspension, so intakes, charge pipes, coolers, downpipes, turbos and fuel system parts are usually listed for both. Body-specific items such as rear diffusers, spoilers and some exhaust sections differ because of the X4's coupé rear. Always check the chassis code shown on each product.

For most owners, a stage 1 software tune paired with a metal charge pipe gives the biggest change for the effort, as the B58 responds strongly to boost and the factory plastic charge pipe can split once boost increases. An intake adds induction sound and response, while uprated brake pads suit the car's weight. Plan your next steps early so parts such as downpipes and cooling work together.

Not for stage 1 or most stage 2 setups on petrol. The B58's factory fuel system generally copes with typical bolt-on tunes. Upgraded high-pressure pumps, auxiliary low-pressure pumps or port injection become relevant on larger turbos or when running ethanol blends, where fuel demand rises sharply. Your calibrator can log fuel pressure to show whether the existing system is near its limit before you upgrade.

Both are strong platforms. The 2021 facelift brought styling and interior updates, while UK and European cars kept the 360 PS output. Mechanically most performance parts fit both, but some intakes, exhaust sections and trim pieces are specific to pre-LCI or LCI cars, so check the product notes. ECU tuning support can also vary with software version, so confirm compatibility with your tuner first.

Yes. Lowering springs for the G02 X4 M40i are typically designed to work with both standard and adaptive M suspension, so the damper modes remain. Drops are usually around 30 mm at the front and 20 mm at the rear. Have the car aligned afterwards and check headlight aim. If you're unsure which kit suits your car, check the fitment on each product or ask our team.

A sensibly modified X4 M40i can pass an MOT, provided all factory emissions equipment remains fitted and working, the exhaust meets noise limits and there are no warning lights on the dashboard. Sports-cat downpipes must be paired with suitable software to keep diagnostics healthy. Declare every modification to your insurer, and keep fitting records in case a tester or insurer asks for them.