Got a '03 SE/SC with less than 10K on it. The thing makes a noise that can only be described as a metallic "rattle" on acceleration. The dealer had a cat replaced that had broken loose from the exhaust housing, but the noise is still there. The sound can be reproduced consistently at 3000 rpm. Could the SC or maybe some heat shielding be making this noise?

sounds like a heat shield somewhere on the exhaust system..... search in problems and annoyances forum for lots 'o posts on the problem.