Well... Rats. One thing you can try is to have someone else drive the car while you sit in the pass. seat and then also try sitting in the back seat, on both sides. See if that helps you localize the sound. Sometimes sounds reverberate around and you get fooled as to where they are coming from. It might give you a different perspective on the problem.

Failing that, it might be time to take it to a body shop that has experience with these cars and let them have a look at it... maybe you can pay them for an hour's labor or something for a diagnosis. Let us know what you find. Pete