Notsure what car you've got, but if you've got a P5, do your spoiler, mine was NASTY bad, even worse than I'd thought from inside. I still get rattling from that stupid plastic lisence plate holder but I'll soon delve into that. Gotta edead my hatch as well. My 1100w ELemental makes the whole back of my car visibly vibrate. In fact if it's bumping good my rear-wiper skips all over the place... Butyes, if P5, DEFINATLEY do your spoiler. I think it shoudl be in the how-to section or something. It's actually fairly simple, and the problems become apparant. 2 large pieces of plastic that prettymuch just sorta touch eachother and glass. I used a good bit of weather stripping and my personal favorite, Bicycle handlebar tape... Ahh, the neverending quest for a rattle-free car.