What I noticed during the CIC retrofit is the two nuts that hold the center AC vent can come loose. As Dave said, if you remove the carbon trim and tighten the two bolts it might fix, if the two are the culprits. I've had the car for five years now, and apart from that, and that too being my fault, no other rattles ... touch wood!! Hope this helps.
2007 E92 6MT - Silverstone II with /// Performance Exhaust with ACM Test Pipes and BPM Sport Stage II Dev-Tune
2011 F25 X3 3.0d