It's a BMW diesel "problem" and I've had a 330d ingest a flap in the past. Luckily the car was still covered by BMW warranty as it needed 1 piston, a head, 24 valves and new inlet manifold. wouldn't have been cheap.
I've de-flapped my current 330cd and would recommend it to anyone. Used the PMW blankers and the car is quieter at idle without the 6 flaps rattling away and it also revs more cleanly and quickly.