This illustration shows the wiring scheme of the Ford 4 pole starter solenoid -

The "I" post referred to in one of the previous notes, is being back-fed from the (+) terminal of the coil when the engine is running and the ignition is on. It will be on the down side of the ballast resistor. The jumper from the "I" terminal to the coil gives full 12v+ ignition power to the coil at start - and is isolated after that - otherwise it would defeat the ballast resistor.
The lower voltage may slow the choke opening a bit and the alternate current path will certainly steal some coil power.
I've got my bird wired so that power from the ignition "on" terminal (that used to go to the ballast resistor) now goes to a 30 AMP x 2 pole Bosch "plug-in" relay - and the choke. Main power for the relay (the switched lead) comes from the starter soleniod battery post on a big wire - half goes to the electronic ignition box and the other half to the coil.
Steve Metzger Tucson, Arizona