Well got my 36 sq feet of damplifier pro last night and put it all in the trunk within 3 hours. Gotta say, not impressed. Didn't kill the exhaust note, in fact barely noticable difference. I might buy a little more to get ever nook and cranny (didn't have enough to do ALL of it, just about 87% of it.) and put some spectrum on and see then but I don't know man. If $150 worth of this stuff barely did anything then IDK.

Before I added the resonator to the Zilla'* exhaust (94 was the first year for a resonator, so the Zilla didn't have one) I added household HOME carpet padding under the trunk carpet. It made quite a difference in the damping of the resonance from the exhaust.

If you're looking to block outside noises, carpet padding or dense foam are your best bet. Sound dampening products like damplifier merely add mass to the metal/plastic to lower the resonance frequency. It won't do much to attenuate noise.

to kill the exhaust note you need to do more than just the trunk. Seeing as how your exhaust goes all along under the car, you will need to do the floor of the cabin also.