I will bet on the exhaust leak my daughters cavalier does the same thing .I haven't been able to get that thing to seal since I changed the muffler .sometimes I get it just about sealed and it rattles loose again..
How dide you fix the leak if it is one of those patch kits forgetaboutit they dont work.

Ray
Learn to let go of what does not serve you ,but forces you to serve it
why does everyone ask if I am gonna paint it ?