The PCM is located behind the battery. Unhook the main wiring plug. Look into the female side. If you see any terminals that are not round. Take a very small screw driver and
gently bend them back to a round shape. Then see if the problems go away.
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93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed