BMW 4 Series (F3X) 2016> 420i (B48) 181bhp remap figures

Who is the Stage 2 map for?

• Owners who have fitted, or plan to fit, supporting parts such as a freer-flowing intake and exhaust.
• Enthusiast, track and competition cars: Stage 2 is intended for off-road or competition use.
• Drivers who accept that a bigger gain means more of the car has to be checked and prepared first.

What Stage 2 needs

Stage 2 is written around supporting hardware. For an engine like this one that is typically a freer-flowing intake and a less restrictive exhaust, with the engine in good mechanical order. We confirm the exact parts for your car before any work starts.

• A diagnostic check and a read of your ECU come first.
• We look at the condition of the parts that will carry the extra power before we quote.
• Stage 2 is intended for off-road or competition use.

What this means for your 4 Series

Without a turbocharger the improvement comes from ignition, fuelling and throttle mapping rather than boost, so expect a smaller but still noticeable change in response.

Engine management is by a Bosch MG1CS003 unit. Newer ECUs often protect their software, so we read the exact unit and version on the car before confirming the figures on this page.

We remap at our Belgrave Gate workshop in Leicester, or at your home or work within 30 miles, and every job starts with a diagnostic check.

Please note: these are expected figures, not guarantees. Real results vary with the condition of the vehicle, the ECU software version, fuel quality and the hardware fitted. Some options - including Stage 2 and anything that needs extra hardware - are for off-road or competition use only. We check every vehicle first and confirm what is achievable before any work starts.

Figures reviewed 22 October 2026.