I buy a new engine harness from Year One and then cut it apart and modify it. The wires going to the ballast resistor are tied together (IGN 1 and IGN 2) and that tied circuit is what the Sniper and the Hyperspark plug into. That gives the EFI system a solid 12v both cranking and running. I also modify the alternator circuit if doing a Denso swap since the external voltage regulator goes away. The coil wire is removed from the engine harness and depending on the make and model there might be some other changes.
Other people solve the problem in other ways. I've seen some clever solutions and a lot of hackery.
