There is a great deal of misunderstanding about the sound deadening process and which products to use. Dynamat Extreme is expensive, because it is one of the best. You can find it at Amazon in Bulk Packs for about 1/2 off retail with free shipping. That makes it one of the most desirable products out there.

The job of these self-adhering butyl pads is to dampen panel resonation and to a lesser degree block noise and heat. The do the first part of the job very well, and you don't need to cover an entire panel to effectively dampen the resonation inherent to it.

If used to completely cover the floor, ceilings and doors of a car you will get a moderately good heat and sound barrier along with a high degree of panel resonance dampening.

The secret to doing an even more effective job at blocking heat, fumes and sound is after you put your Dynamat or other product down, is to completely cover the floors, doors, and ceiling with a product like "The Insulator" from Aircraft Spruce or a similar product from Speedway Motors. Cut out all the various shapes that are needed to fit a complete blanket of this stuff inside the entire interior of your car and tape up the seams with that aluminum ducting tape with the wax paper peel-off backing. You may have to use some contact adhesive to keep the stuff up on the roof until you reinstall your headliner.

Once you have used both products and reinstalled your interior, your car will be quieter than any new high end car save a Rolls Royce or Bentley.