The BMW X3 3.5i 306hp (F25 - 2011 - 2017) produces 306bhp and 400Nm in standard form. Our Stage 1 ECU tuning file raises output to 365bhp and 520Nm, a gain of 59bhp and 120Nm, with no hardware modifications required. The file is delivered through the ByteFLASH portal and is ready to write to the vehicle.