grncobra,
the Dynamat works but i am not convinced it is the best solution. certainly not the cheapest. i have about $300 in dynamat and more in closed cell foam behind the headliner. i would be curios to try Lizard Skin or something, but i have blown my sound-deadening budget. my next step is to 86 the flowmaster. that will definitely make the truck quieter, and i need to replace the pinch-weld seals at the door jams. that will help too.
if that isnt enough, i will try more sound deadener! (or earplugs!)