Or do what I did! Just go down to your local wreckers, find some old town cars or anything for that matter and rip the carpeting out, and take out what's underneath. The nice padding fits well under stock carpet in your rig. If the stuff is wet, dry it out first, since a lot of the wrecks you can pull out that stuff get rained on a lot. I was sick of my engine noise running into the car and ruining my audio quality. As for the firewall, get the Dynamat, its cool stuff, but you won't hear too much difference, it will just muffle that badass filter suckin' in the air and freein' up that hp.
steveo
If you are looking for a quick/inexpensive solution, all my suggestions take a little bit of time, thats it, as most wreckers will let you take that stuff for free 'cause it's not metal! Doing your doors and firewall is a little tricky, but we all have common sense right?