If you start it and it idles for a short period 800-900 rpm and after that it drops to 500-600 in LHM, can indicate that the faulty bank is firing during startup. When starting, all injectors will work (despite all sensors/MAF) to make the mixture rich and enable it to fire up. When the DME's notice the engine runs, this startup mechanism switches off and the engine control management takes over.
If this is the case, most likely its due to one of the sensors. Have you tried swapping the cilinder identification sensor yet?
Have you checked the 4 electrical connections in front of the engine (2 crankshaft sensors and 2 cilinder identification sensor connections)?
Keep us posted.
Sean750
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hier der komplette lange thread
http://bimmer.roadfly.com/bmw/forums/e32/6899215-1.html