I frequently get a light sulfer smell, similar, but not as strong as the rotten egg smell I got in the dying days of my 89 740 when the catalytic covernter needed to be replaced. Initially I thought I was just getting exhaust from other cars when the fresh aire vent was opened, but now I'm getting the smell move frequently when the internal air cirulator is in operation. Since I don't have any warning lights, could this be the catalytic converter? I know that there are sensors involved that are supposed to pick up various problems and should initiate a warning light. Since the smells come and go, what do I tell my service guy to look for. Any thoughts/suggestions are greatly appreciated.