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.
E92 M3 2007 - ///PE with Test Pipes and BPM Stage II; CF Interior & Splitters; CIC with Connected Drive