I don't think your problem is from a BAD MAF. Unplugging the MAF just default the engine to run on its pre-determined fuel/air maps. When the MAF is plugged in, your DME/ECU is using realtime data (air flow) to calculate the fuel/air mixture.
This is the reason why your car doesn't go into limp mode with the MAF unplugged.
VDO/Siemen is the OE supplier to BMW for its MAF. Therefore, the likley hood that your new MAF is also defective is unlikely.
Like everyone said, just get a diagnostic because solving this complex problem will be difficult w/o a scanning tool. BTW..autozone offer free SES/CEL scanner assuming you have an OBD-2 port and not the older BMW DLA port (cicular plug located in the engine bay)
I hope this helps, good luck!!
Last edited by flashmeow; 10-26-2012 at 06:14 PM.