IDK Orero, I have not heard of this kind of rattle.
So... you turn off the car when its fully warmed up, and then let it sit parked for a few minutes, then start to drive and you hear the WG rattle? Or do you hear the rattle before you drive off ?
Have you had the HPFP recall/SW update done? I know it kills the throttle response... but it also changes the WG duty cycle at idle and off idle. It really makes the injectors and WG run MUCH quieter. But I hated it for the crappy throttle response - so I went with a flash tune.