Let me tell u what i did. I stripped out all my interior. Went to wal-mart and bought at the automotive department some rubber spray. And i bought a bunch, like 6 cans. I went home and dowsed my truck interior. Carefull not to get rubber on somethin you dont want to get messed up. When done sprayin let it dry and air out.
There's some roofing material I read about somewhere (here?) a year or so ago that's like the same stuff as Dynamat but a LOT cheaper.
Can't remember the name or details, but it's on my computer at home. I'll try to find it tommorrow.
ahah my first post was goin to be the b-quiet!! aha... its cheaper and by far more productive!! the only diff in the dyna mat and the b-quiet is teh addhessive on theback... but is by far worth it, it wont only stop some rattles but make it louder and cleaner.. ull notice it!! hhope this helps a bit