Could be a DSA valve. Needed mine replaced around 100k. I had similar symptoms which were a rough idle after the engine had fully warmed up. Engine speed would fluctuate between 600 and 800 RPM (M54 - 530i). Did not throw any messages in iDrive until I was taking the car in for repairs (what a coincidence huh).
2004 BMW 530i (his) -Titanium Silver -Grey Dakota -Dark Poplar -Premium -Sport -Cold Weather -Xenons -Heated Rear Seats -Active Steering -Logic 7 -Sirius
2010 Lexus RX350 AWD (hers) -Smokey Granite Mica -Black -Premium -Comfort -Nav -Tow Prep -Premium Sound -Wood Steering Wheel/Shifter
Last edited by dwlink; 01-11-2013 at 03:49 PM.