I need some help. When I get to about 1500 rpm's there's an annoying rattling coming from the bottom of the Jeep, and I am thinking it has something to do with the muffler. I've read a couple threads say it could be the heatshield, so when I get off today I was wondering if someone could help me locate where the heatshield is so I can see if that's loose and causing the rattling. If you guys don't think that is it, what could it be?? Thanks!