At some point, might be the ballast, the dark blue "run" splits off and feeds several circuits. BEAR IN MIND this is not fused, so don't get sloppy.
Depending on year/ model, dark blue or "ignition run" feeds ballast to coil +
ECU power
VR power
light blue ends up at alternator field
electric choke if used
some smog doo dads on some years
I would carefully cut open the harness and pull the ECU wiring out