I don't hear the rattle either. Only thing that sounds wierd is your BOV and when you shut off teh engine that wierd sound.
What year is your car and how many miles? Why wouldn't said sound be covered under the powertrain warranty? Have you contacted a dealer to have a RSM (Regional Service Manager) listen to your car?
IF the sound you are describing really is driving you nuts... have you thought about paying your dealer for the SW update that gets rid of the WG ticking. ? They would probably charge you and hour or two's labor rate for the SW update. BUT... be forwarned that BMW's SW fix will leave your WG open at idle and it will KILL the performance and snappy throttle pickup/acelleration. BUT... it will make your engine quieter at idle. It also reduces the ticking injector noises.
I had BMW update my SW... and I was really unhappy with it. Sure it made the engine quieter... but I never complained about THAT. I mainly wanted the new DSC, TPMS and 6FL, SW upgrade. But it really gutted the performance of the N54. Made it almost feel NA like. No power. To each his own. I have grown to accept the various noises the N54 makes. It comes with all that POWER!