Alright guys, I've been hearing this metal rattling noise in my car ever since summer, and i only hear for a few seconds right after i take my foot of the throttle. I've always thought that it was my exhaust pipes rattling against hte heat shield, but yesterday while checking under the hood to listen to how loud my valves are ticking (very loud i must say) i noticed it actually was coming from the block!! It only happens when i suddenly take my foot of the gas, and sometimes when keeping a very low, steady, rpm. Its a rattling, clanking, grinding type noise sorta like someone has a cup with a marble in it and shakes it up. Any one have any idea what the heck this is???