I’d check connector cn11…looks like pin 2 or 3…schematic is fuzzy. If the coil is working intermittently, I’m thinking it’s connector is loose or perhaps a cold solder joint. Flex on that connector while in coil test mode firing the coil in question. If it works you found your problem. Then put your old more powerful coil back in so the ball makes the journey to the trough. God speed!