sometimes the heat shield needs to be bent further from the exhaust... my car had an annoying rattle, at 1,200 RPM... i thought the exhaust bolts needed to be tighten, it worked then later on it rattled again, but eventually i found the exhaust rubbed against the heat shield, and i put a breaker bar between the exhaust n' shield n' pulled them apart the bend the heat shield away from the piping and it solved the rattling problem.