I had a like problem with a 02 800 m.c..I finally came up with a bad volatage regulater. My daughter noticed that the tack would go crazy when it would act up. The problem was very intermediate and would happen mostly under power situations. I had already checked everything out. The voltage regulater has three wires on it (I'm guessing you have a E.F.I. sled). so the red one feeds the servo motor. So the power valves didn"t work all the time. The voltage regulator converts ac to dc for the motor. But this only true on EFI units. On carbed models there is another type of voltage converter to do the same thing for the motor. Hope this helps out.