I have a really nice '89 190E 2.6 and I want to know how to tune it w/o taking it to a mechanic. I'm fairly handy mechanically and have the tools (I think). Also, the car is giving off a very strong exhaust odor when idling. And finally, the oil pressure gauge moves to zero when I come to a light or when the car is idling...is this something to be concerned about?