yea do the search there are like 15 threads on this topic i had the same problem u found one imparticular real helpfull he listed everything from the dynamat(def want 2 layres all over and a solid 3 on the lid itself) also extend the little trunk lid stops out, put a stick on weatherstip on both the lid and frame, if the plates causein problems dynamat the back of it and use rubber washers on the bolts, and oddly enought it helps but put about 3 layres of elecrical tape on the piece that the latch clamps down on. im rockin 4000 watts and its pretty much tamed
Search for posts by me....I compiled a list of problem areas to work on....
but for sure, you'll need more than one layer of anything you use, and you
need to focus on certain areas more than others, including underneath
the car in the area between the rear fascia and the bumper (just behind
the license plate area).