As for the rattling sound, it could be many things. First off, if you can get under the car or get it up on a lift, I would check the exhaust system components such has hangers and U clamps. Also make sure that none of the exhausts system pipes are touching the frame or body. Even if everything looks good, there could be the possibility of one of the interior baffles in the muffler may have come loose, and is causing the sound you hear. If everything looks good from underneath, I would check the engine compartment to insure that all the components are securely fastened. Good luck!!!