When I was demo'ing my 75, My mechanic borrowed a box that we hooked to the diagnostic plug on the left side of the engine; right above the computer module. Seems I remember that thing giving readouts of all sorts of things, including turbo boost. We hooked it up, and ran the wires through the windows, so we could keep track of things as we were working the tractor in the field. The electronic engines process a lot of info, in order to keep running at max effeciency. The right box lets you look at what the computer is seeing too. I suppose a bad sensor might confuse the computer and cause some of your problems too. Ed in Montana