I found a quick way to get a lot of rattles out of my car w/ no money down. I took off the housing under my car that holds the fuel pump and dumped out all the dirt. There was a lot buitlt up in there. It takes a torx head to gett it off. You can also reach up under the bumper on either side. There are 2 vents for the trunk and the cover will pop out and pop back in. There was a lot of dirt there too. I don't drive in mud all day but I guess it builds up after a while. After I did this my sub sounded much better from the outside and it was all free!!
