[mobius911]

If the electrical system is not working 100% it can give you fits. I've had CDI boxes that worked fine until the car got to full operating temperature, then they started malfunctioning. I've heard the same can happen with the Pertronix.

You may be at a point where you need to swap in known good components on the ignition system to see if something there is causing the problem: CDI, plug wires (seems they are good so that's only a last resort), cap/rotor, Pertronix, coil.