Well yesterday I replaced my valve cover gaskets and also put on the muffler that came with the car I purchased. Strangely enough now though when my car is running and I push the clutch in or put the car in neutral it revs up to like 2K rpm's and continues to rise. It was "idling" at 3,800rpm at one point. I don't understand what happened. First thought was that it had something to do with my exhaust then after that I thought it might be my throttle positioning sensor. Any ideas on this??