What could a bad regulator potenially destroy?

It's a 4 pin, and I switched to the two pin ballast resistor. I measured from the coil to the harness to see which one was supposed to be connected. I was having this problem a few weeks ago with the car. I replaced the ECU with the one off my truck (put a new on on the truck), and it ran fine for a few days and now it's dead again. The ignition module (ECU) measured bad again so I figured something burned it up, that's why I checked out the voltage regulator. I'll have to check to see if the coil is getting voltage or not while its cranking. The air gap should be OK, I haven't ever messed with it and I don't see how it could have changed. I'll measure across it while cranking though because I know they can go bad (it measured 300 ohms sitting still).