You have ALOT of leeway on how little ballast you can get by with (always carry spares). it mainly depends on the coil selection as to how much ballast you should run & much less on what ECU you are running tho the ECU has to on/off switch the amount of current in the coil primary circuit which is the sum of your coil/ballast choice & will be affected by your choice of ballast in the long run. 35 yrs ago I ran an Accell super coil (the big yellow beast) with no ballast (OE 70's electronic dist/OE '75 chebby black HEI module) with no failure & it ran awesome. (Accell later told me to run a .7 or .8 (I forgot which) ohm ballast with that coil. Jacobs the ign people tell me that too much power can actually cavitate A/F molecules out of the spark plug gap