Metal rattling
 

it almost sounds like the heat shield on a cat but i checked them and nothings loose. It happens every now and then when accelerating. havent heard or noticed it while at a constant speed. any ideas?

Could be the honeycomb of the cat broken off internally. I usually just punch around the exhaust and see if I can replicate it.

so what you're saying is i should just gut my cats? :D

I didn't say nothin! :)

to do that you would need a tune or o2 sims. But if its the cat going bad, I would replace it.

Check above the rear axle to see if its hitting the upper panhard bar. Without hearing it, and with your description, its going to be a shot in the dark for everyone.

Check all the heat shielding along the floor to see if any of the screws came loose. Then I would get it up on ramps and try hitting the exhaust to see if any of the clamps or connections might be coming loose.