yes the 85+ spoilers rattle with lots of bass. Its mostly where the two halves of the wing screw together, you could take it apart and put some wetherstripping in there or some kind of deadener, or just get smaller speakers with less bass, stereo equipment just slows the car down anyway , might as well put the least ammount in there as you can stand, or just get a nice exhaust and listen to that.
Wal-Mart sell 8.5"X11" sheets of sticky back foam for less than $2 each. The foam is thin, and you can get it in black. I have used it on several liscense plates to keep them from ratteling, and it works well. It dosen't seem to be affected by rain/washing.
First you have to get it off the car. There are brackets on both sides with 2 10mm bolts each and there are 4 more 10mm bolts under the trim panel in the back where the light is, there are 2 bolts in the center and one at either end. Once its off the car the 2 parts of the wing are held together with what seems like a million phillips head screws, thats pretty much all there is to do, just make sure you have an old blanket or something to set it on so the paint doesnt get scratched while you are working on it.
theres really no need to add foam, just get some dum dum (a tar like substance, kinda sticky, somes in strips, the guy at the store will know what it is...) and stick it between where the top piece and the bottom piece meet all the way around, then put it togeher, tap it, and put some between the top and bottom where it still rattles by the screws.
This kept everything pretty light, and nice and quiet.
Oh, and watch those aluminum screws, make sure the screwdriver fits them near perfectly, because the buggers like to strip.
Me and a friend of mine tried to remove the spoiler and took off all bolts listed above but we could still not remove it. It seemed to be attached near the top(were the hatch and roof meet) is there something im missing or does it snap off? Or do i have to remove the whole hatch first?