Pertronix, the manufacturer of the electronic ignition (EI) offered in the MMI catalog has really stepped up their game over the past decade or more regarding issues and troubleshooting. Check out this advisory paper from Pertronix themselves. The entire treatment is filled with pertinent information but of particular interest to previous discussions on this forum are the sections "My Vehicle is Misfiring or Breaking Down Under Load" and "What Type of Coil Can I Use With the Ignitor™?"