Well, I would consult some experts. In other words let this thread simmer a bit, let some guru's confirm my suspicions... I am pretty sure they will tell you one way or the other. Once you have it narrowed down, hit the dealer and say, "Yeah, I'm pretty sure the XXXXX
has gone bad, can you take a look at it?"
I also highly suggest you do a search on 'sulfer' or 'exhaust smell'. I KNOW you will find many threads there concerning this exact problem. I have seen many sicne I got here, I just can't remember off hand what the cause is.