Dynamat Question

It should make it quieter outside of your car.  Some of the bass sound you hear outside is from the panels actually vibrating like speaker cones.  Dynamat will reduce that, as well as reducing rattles from interior panels, license plates, and things like that.  As for your exhaust, I'd investigate that further and find out just what it is that's rattling.  In a properly-installed exhaust system, it should be supported solely by the rubber insulating hangers, so there shouldn't be anything making contact to rattle.

As for the best way to use dynamat, I'd concentrate on the big, flat panels first.  I usually put a double layer of Dynamat Extreme on the roof, floor pan, trunk floor, and undersides of trunk lids.  For everything else, a single layer will probably do.  You don't have to cover every square inch of a panel to make the Dynamat effective, but the more panels you can cover, the better off you'll be.  In an extreme install, it's not overkill to apply Dynamat to the inside of fenders, inside of doors, etcetera.

After you're done, make sure you save a little bit in case there are any small rattles left over.

Scott Gardner