Basically I ripped the guts out of my old car stereo an installed them in my '02 WRX. The dash is still all ripped apart because I can't find a store that sells the piece that holds the head unit in place. Basically it's just sitting in the cavity where the stock unit was. Anyway, I had a Jeep before so the Dual 12'' subs don't fit the best in my trunk but I make do. It sounds pretty good, too, but there's this god-awful vibration coming from the trunk that I just cannot get rid of. It seems to be worst when the trunk is closed, making me think it is the lid. I was going to buy some of that sound deadening stuff they sell at Best Buy and stuff it in the trunk lid, but I don't even know if that's the problem or if it will help.
Oh, and it's not the license plate which also vibrates but is tolerable. Whatever this is is much louder and much more annoying. It's really ruining my listening experience. Suggestions?