Hi Mike, Two things concern me. First the amplitude of the signal just pre and post tdc should be the same as the rest, shouldn't it? I couldn't think of a problem that would give variable amplitude from the crank sensor, apart from large crank end float, and I assume the problem was caused during the head gasket change. And when you say CPS, you mean Crank Position Sensor, and not Cam Phase Sensor. Just wondered if plugs could be interchanged on this as can't think of layout at the moment! Can't wait to hear the answer!! Regards, Nick Bell