Suggest using a rubber mallet and tapping all around the area where you think rattle is coming from. For me I discovered a rattle of mine which I originally thought was engine-related actually came from within headlight.
I did this and it seem the bit on the exhaust that moves ie the part of the exhaust the side exhausts connect to does make a rattling sound when it with the rubber mallet but the passenger side doesn't. Looks like something I have to put up with.
