Lately I've noticed a buzzing noise coming from somewhere in the front. Sounds like metal on metal buzzing. It's very noticeable when the vehicle is cold and gets quieter as the car warms up. It also seems to clunk when I hit a bump. I was thinking heat shield but the location of the noise tells me otherwise. It's coming from the front right of the car, not sure if it's outside or inside the cabin. Any ideas?? I noticed that consumer guide says something about a BTV valve that sometimes rattles on the 2nd gens. What's a BTV valve?? The noise is getting very annoying!!!