I had the car apart the other day installing my 6 channel amp for the mids and highs. Ran out of time and I got the interior back together with the exception of the two side panels that go next to the rear window, above the rear deck that cover the airbags. I noticed that no matter how loud I turn the bass up, there was no rattle at all. It sounded 10X better. I reinstalled the panels today after a week or so without them and the car is back to being a rattle trap with the volume turned up. At least now I know where to concentrate on fixing the problem. The rattles we all get are where the rear deck contacts the side panels. Wedging something between the rear window and deck helps but it's not actually where the noise if coming from.