I have two problems, the first is my truck will shudder when rolling into the throttle just as it starts to build boost. but if I floor the pedal it will run fine. I have replaced the lift pump and added a pusher pump on the frame next to the tank and the filter is new. The second problem just start and I wonder if the two might be related. The truck start running very eradict like something was taking the injector pump to WOT only for a split second, then I noticed that the tach was swinging from zero to indicated rpm. I would expect that the tach pick up sensor is going bad. Can the sensor get dirty or do they just wear out? Thanks in advance.