Many coils are advertised with open-circuit voltage claims of 40,000 volts, but it is a useless number. Usually, the actual firing voltage is determined by plug gap, cylinder pressure and temperature, along with plug electrode type. The usual engine needs about 10,000 volts to fire a cold plug and a bit less when warmed up. Stock coils will work just fine for street driving, and any misfire problem will likely show up as you operate at higher rpm at WOT. Then you have to decide if you want to change coils, or get a dwell extender or some other solution.
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