Link to Graham's solution for exhaust drone on the Corral
This is probably the best solution for you if you want to eliminate exhaust drone.
All other solutions seek to reduce transmission of the noise by "deadening" the metal of the car (turning sound energy into heat energy). This solution by Graham seeks to cancel the sounds before they are transmitted through the car.
If you choose sound deadening material, then before you make your purchase BUY THE SAMPLE KITS!!!!!!!! This will help make the chioce an easier one.
Most of the sound deadening products are identical in nature and construction. Do you think all these companies have research labs whipping up these VB suspension formuals? Probaly not, They're likely buying from the same source with different labeling. Thats why they look the same, come in the same dimensions, and those that print statitics have similiar results.
I choose the products that I installed based on a comparison test done by a British magazine. They did transmission tests using all the popular products and the Brown Bread (now replaces B-Quiet Extreme) came out on top. This was due in part to it's attractive price and reduced sound transmission.
Not one of the posters here has provided a bit of information regarding the drop in interior sound levels pre and post install. Why would you take any of that advice then for your problem???? Minimal as it is, at least I have some data on that SoundDomain site (page five).