The Germans at Hartge released an engine conversion kit for the BMW 1-series M135i and M135i xDrive.. The conversion increases the maximum power output by 13% from 320hp to 367hp. Furthermore they have upped the maximum torque from 450Nm to 520Nm.
Finally acceleration from 0-200km/h is improved by 3.08 seconds.
Hartge Engine Conversion for BMW 1-Series M135i