Martin, mach das Ding Geraeusche?
Falls ja, Stecker abziehen, wenn Geraeusch weg, DISA defekt

Hatte mich selber in den letzten Wochen mal darum gekuemmert und folgende Info in Englisch gefunden, hier kopiert:

http://www.youtube.com/watch?v=HACtkT87PKc

" DISA VALVE FLAP BREAKS: the DISA valve flap breaks, sometimes with parts sucked into the intake manifold (1) (2) (3) (4) (5) (6) (7) (8) or the disa valve o-ring fails (1) (2) & where to get just the DISA valve o-ring (1) & when the DISA valve flap closes (1) (2)"
scrool down here to see a video of DISA valve repair DISA (DIfferenzierte SAuganlage - "Differential Air Intake")

http://www.bimmerfest.com/forums/showthread.php?t=514543

The DISA (according to BMW) is CLOSED at low RPM aka energized. A vacuum is formed to force the flap closed.

You should see a small hole on the side of the round portion of housing. Force the DISA flap closed and hold it (you will feel the spring tension). Put your finger over the hole and release the flap. The vacuum you created by plugging the hole should keep it from fully reopening.