when i got out of work tonight i fired up the ss and heard a rattle right when i fired it up! i revved it a little, and the rattle was still there, but only when i revved it! not at idle or gradual rpm increase! then i went to leave and as i went forward it sounded like an exhaust tick but went away as the engine warmed up! my CEL isn't on! and it seems to be running the same! 52,000 miles! any suggestions?