My car has this howl after the car has warmed up. It is a continuios sound coming from the mid section of the car. Also there is rotten egg smell coming from the cat, I think. I'm not sure if it has anything to do with the cat. The howl happens at 10km or 100km at park, netruel or reverse. It does not effect the performance of the car and I'm told it has nothing to do with the trany pump. Really confused, can soemone help!! dunno powersix