One gripe I have about the Pertronix systems I've worked with- - - - -the trigger assembly that slips over the cam that normally would operate the points is a VERY sloppy fit- - - -which could, and probably does result in a degree or more of variation in spark timing between cylinders. This problem could very well be the source of the rough idle the OP mentions. That error would also be totally random- - - -no way to adjust it out for a more accurate spark. If someone insists on running that ignition system, I'd strongly suggest gluing the trigger onto the cam assembly with some sort of stuff like epoxy or LocTite. Of course, that would make an emergency swap back to points in case of a breakdown extremely difficult.
Jerry
