Squeaking and vibrating of rear deck against rear windshield w/ sub hits!?

[BlueIce]

I know someone who has one of those expanding foam sprayers in his machine shop. If I were able to use it, exactly where do i spray the stuff? Would I have to remove all the trunk carpeting etc.? Can it be sprayed inside the actual trunklid?

I also noticed a very loud rattle coming from something inside the rear bumper. Holding the bumper doesnt stop it either, it sounds like its right above the gas tank, anyone know what it could be?