The BMW Z4 3.5i - N54 - 306hp (E85 - 2003 - 2008) produces 306bhp and 400Nm in standard form. Our Stage 1 ECU tuning file raises output to 370bhp and 500Nm, a gain of 64bhp and 100Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.