BMW Z4 (2003-2005) MS45 ECU Tune - Stage 1See our full write up for more details and other tuning options! Stage 1: This is our OEM plus tune, ideal for a naturally aspirated engine with modifications ranging from stock to full bolt on. Expect approximately +15 horsepower on a completely stock car, and more with additional modifications. Full and part throttle tuning is optimized through adjustment of VANOS, ignition timing advance, engine torque request, throttle response, lambda targets,