I was travleing home tonight and i stopped at a light and something was rattling. the first thing that came to my mind was my exhaust. i have hahn and it likes to hit were it goes over the axle. i went and wiggled it and it went away. well when i get closer to home my car sounded like it had a hole in the muffler. around 4grand it would sound like **** right underneath me. It sort of sounded like it was only running open downpipe. Got home looked underneath the car and everything was together and the noise went away. any ideas what it could of been