Sound Deadening

I'm In the same boat, and it depends on what you want to spend. No offense to those that used it in their high buck builds. Dynamat etc. is about 5 times the cost of the Home Depot / Lowe's Air Duct Wrap. I'm going to use that. For extra insurance, use 3M glue for extra adhesion. As for as the butyl vs. asphault based equation, I figure heat will only be a small problem, and how close offending devices will be to the floor pan in the first place.

Google this subject, there's plenty of coverage on it. Here is one instance:

http://mustangforums.com/forum/clas...d-deadener-kit-insulation-undercoating-2.html

IMHO. Save your upgrade-to-dynamat-cash for something else. If it "fails", what's it going to do? Come unglued? Who cares. its on the floor.