Electric Choke

The blue wire that plugs into the inlet side of the ballast is a 12+ source from the ignition switch in the "run" position. This would be the easiest place to get your 12+. You can run a new wire from this location to your electric choke with your inline fuse holder. I don't really thing you need a relay on this small circuit but you can if you want to. Just use your new wire to activate the relay and run a second wire right off the alternator + stud to power the choke.