I have a exhaust fume smell with the heater on and the car at a stop. I was told it could be the variable timing unit on the back of the cylinder head leaking a small amount of oil onto the pipes and making the smell anyone ever run into this I do not want to spend the $500 on a guess. To me it smell like exhaust not burning oil but I have been wrong on other things. By the way it is a 2005 A4 1.8t Cab.