bitch. that's right, it rattles hard out. as a not very smart car person, how do i fix this problem? it used to have a nice growl.. now it's like a chainsaw ripping through sheet metal..
catalytic convertors may have collapsed, try shaking the exhaust with the car not running and listen to where in the piping it appears to be coming from, and even try gently tapping the cats from underneath to try and diagnose....
can also be a manifold gasket. But that would sound like its coming from the back of the engine / underneath the car...
I had a similar problem sometime after replace mufflers. On cold engine it was O.K. when exhaust got hotter it started to rattle, especially in hot day. the problem was in settings and in thick robber O-rings holding a muffler and exhaust pipes.