Torque to the spec of your vehicle, aftermarket wheels do not generally require any special torque figures. In this case, the Z4M is 88.5 Ft-Lbs I believe? Maybe someone else can confirm (or check door sill tag, I think it's there?). I will generally torque to 90 Ft-Lbs, and imagine the average torque wrench has a small margin of accuracy.
Post some pics of your car on the BBS if you haven't already
