In my '97 B4 (VR6 - 52,xxx miles) I have started to get an intermittent rotten egg/sulfur smell inside the cabin. I have noticed it the last couple of days after pulling into my driveway, and this morning just after I parked at the park n ride. Could this be anything else but the catalytic converter giving up the ghost? I have no CELs or other indications that something is afoul in the emissions system. The car easily passed state inspection in November. Any ideas?