Just a stab in the dark, but it could be a TPS (throttle position sensor). I would say pedal position sensor but I dont think BMW started useing those until 98. If the 750 is "drive by wire" then I would say pedal position sensor. Take that with a grain of salt. Although I have been working on cars sense I was 13 (41 now) and an aircraft machanic by trade, I have never touched a 750.
Hope this helps and good luck.