Ballast Resistor

... A coil on plug ignition can be superior to a CDI, much more reliable.
Yes, because each cylinder then has a dedicated coil, allowing more time to "charge up" between sparks. Actually, magnetic field energy, but "mag up" isn't a term. But, to use a COP system requires a crankshaft trigger plus camshaft sensor if you don't want 2 cylinders sharing a coil ("wasted spark" system). Many fit a 36-1 toothed crank wheel to drive a Ford EDIS (1990's). Better are the integrated coil-driver from a GM LS engine, but I don't know of any off-the-shelf system to trigger one (Mega-jolt?). The megasquirt site has much info.