The BMW Z4 2.3i 204hp (E85 - 2003 - 2008) produces 204bhp and 250Nm in standard form. Our Stage 1 ECU tuning file raises output to 225bhp and 275Nm, a gain of 21bhp and 25Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.