No worries on the confusion...Im just trying to make sure I help the best I can...

B_Quite is fairly inexpensive stuff to begin with....not too sure what else to try. I have seen guys use house insulation, egg crate style foam, carpet padding, various foams from a fabric/hobby store, and things of the like. Not wil work quite as well as some of the specific "absorbtion foams" but it all helps.

You might want to look at McMaster-Carr...they have some pretty interesting items. Some chaper, some not so cheap.

Where did you put the 3 layers? just the trunk? the whole car? Just because the exhaust is (basically) unter the trunk, make sure to dampen the rest of the car as well. Typically, the roof is the largest piece of flat metal to a car, and therefore (typically) the easiest to vibreate/resonate...