I agree, it is a power supply problem.
I was having alternator/batter issues on mine. I was going to drive it to work one day, and it had been on the charger after an alternator replacement. Drove to the gas station a mile or so from home, and left it run when I went inside. When I came back out, the truck was running, but when I got in, I noticed the indicator lights were off, I.E. - The Parking Brake indicator light. Once that caught my attention, I noticed all the gauges were at their "Zero" mark. At the time, since I was having trouble, I bought a cheap, plug into the cigarette lighter plug volt meter. Not a perfect solution, but better than nothing. I looked at the meter and I was at ~9.0 Volts!!!!!! Had the "Oh S**T! thought and drove straight home. On the trip home the alt would come to life a little and the gauges would start working, then die, then work..... Replaced the alternator, again (Was a defective replacement), and all the issues cleared. I am not sure if/how the performance was affected since I was still in town, and I was babying it home.... However, during this same time frame, while I was having the alt. trouble , I did have the voltage get to a point it turned the battery light on, it was still in the 12v range at that point, but it still ran correctly, had the expected power and instruments still worked. I would say someting is affecting you power supply to the engine/instruments.....
