Hi friends. At a car show on Sunday there was an old school guy with a Sun tuner in the back of a van doing tune ups . He's a very knowledgeable chap. I thought I'd get my 312 tweaked. All was well but while the car was idling the spark plug readings on the screen were completely off the scale. Massive peaks for each plug completely off the top of the screen. Strangely it returned to normal at cruising rpm. This has confused me. Is the oscilloscope showing voltage? Why would they be too high at idle? Plugs are Autolite 45 gapped at 40thou , it is running pertronix igniter and a pertronix coil. I increased the plug gap according to pertronix recommendations. He suggests all the plugs are faulty. Confused.