http://www.amazon.com/gp/aw/d/B00020...ywords=dynamat
People use that if they have expensive audio equipment to keep road noise out or if they have a loud exhuast.
I used it in my g35 when my exhaust had a lot of drone. The best way I can describe it is a rectangular foil pad with a tar like substance applied to the back. It has a wax paper backing that you peel off. The correct way to apply it is to remove the carpeting in your car and the slap the tar side directly onto your panels.
I didn't want that messy stuff all over my car so I just spread out the pads (with wax backing attached) in my spare tire well. Since you're only covering a small Surface area, your not going to catch all the noise, but with the small amount of exhaust from he MPE, I think it should do the trick.