Thanks guys for the info.
What I want to apply the sound damping material to is mostly for the exhaust noise.
I'm just trying to find an inexpensive way to do it.
I just installed Flowmaster DF 40 series mufflers on my GTP and It sounds great. The rumble of the V6 is awesome.
I can definitely hear it when I'm accelerating and all I'd like to do is tone down the exhaust noise on the inside.
Carpet padding is worth try, I'll check it out. And if it doesn't do the job, then I'll try the other material (i.e. secondskin, Dynamat, Dynomat)
Any input is greatly appreciated.

Peace!