it could be the front fender, i had a rattle driving me nuts on my GT, finally figured out that it was the front fender doing it. There are two tabs or two pieces that tabs would slide into on the underside of the fender near the rear just past center, those dont fit together tightly so the fender rattles, just lightly tap on the back of the fender near the bottom and you will hear it possibly. I checked with the dealer and there is no rubber mounts or anything to make that a tighter fit, so i will modify it,