ignition problems

You need to be more specific, or all we're gonna do is keep going round in circles.

Are you trying to tell me you are measuring 13.x volts WITH THE ENGINE NOT RUNNING?

If so, you have something wrong with your meter.

You don't need to trash the harness, you can rewire what you have now.

YES if you are sure you have (and are going to use) a 4 pin box, all you need is a 2 pin resistor.

12.6 at the coil is too much, for about the third time.

One thing that might help is to draw it out yourself.

Draw a picture of the coil, ballast, regulator and ECU.

Start at the ECU follow EVERY wire to where it goes.

Find the blue at the regulator and follow where it goes

Find the blue at the alternator and follow where it goes

Everything should "funnel" to the ballast and the bulkhead

You really at this point might want to find some local help. Surely you have a friend/ Dad/ Uncle/ etc that's good with wiring.

All you need to do is print out one of the diagrams I posted, and follow it.