I know that this is not Z related, but I need advise fast so I am posting this up on every forum I can think of. Please help if you can, I need to have this problem resolved by Friday afternoon. I have a '70 Chevelle Coupe that is making some scary noises. When I turn the engine on the driver's side exhaust rattles at idle. I just had exhaust cut-outs put on so I thought that that side was hitting something, but that is not the case. More recently it has been making even worse noises. It will run for a bit then it will make this loud bang, like somebody hit the exhaust with a hammer. I watched different parts of the car for a bit. It is not a backfire, the exhaust cutout is not hitting anything, only the driver's side rattles while the passenger side stays put. The header is on tight because I just put a new gasket in today. Here are some of my questions. Could putting the passenger side header gasket on the driver's side create this problem? Could the exhaust cutout somehow be the problem? Keep in mind it ran perfect until I got the exhaust cutouts put on and then the rattling started. The loud bang didn't start until I changed the header gasket.