I HAD a rattling problem in the trunk area for a long time, it sounded like loose speaker cover. I brought the car back to the dealer 3 times, but the rattling was still there. So finally I got so fed up, I started to take all the removable parts out of the trunk, including struts that hold up the lid, one at a time. But I still could not locate the source of the problem. I was so fed up that I was about to push the car off a cliff. Finally I took my car to an independent mechanic and told him to find and fix the problem at any cost.
After 7 hrs and $400 later, they found the culprit. It was the right rear light, it wasn't mounted properly. It could be the guy who tinted my light and did not install it back properly. But who kowns and who cares.
Now my car is rattle free, and I love my car again!