1993 ls 400 with new ecu rebuild, new coil paks, new cranksensor. Everything was fine until about 2 weeks later when the car started running on 4 cylinders. Checked timing belt, it was OK. RPM needle is jumping around, not normal. What feeds the rpm needle? Is it in one of the coils, or does it come from the cam sensor? If yes to either one, what coil or which cam sensor sends the signal? I really need some input on this problem.