I ended up having a small rock that got stuck in there. I beat the hell out of it trying to knock the rock loose but I had to take the heat shields off eventually to get it out. Took me forever to figure out it was a rock in there...maybe you should take the heat shields off and check? I know it's a pain, but if the rattle bugs you as much as it did me then an hour worth of work to possibly fix it is well worth it.