The 420a injector harness has one positive wire that is shared for all 4 injectors. The 4g63 resistor pack has one switched 12volt input wire, and 4 separate positive injector wires, each of which go to the 4 injector positive wires. You should not have to even touch the OEM negative wires at all, just the positive ones. Easiest thing to do is to remove the stock injector wire harness and wire loom, and re-wire the positive wires. This doesn't really require a diagram. The stock injector positive wire is a thick green/red i think, it's the only thick wire in the injector harness. Cut that wire on the injector harness clip side of the harness main connector(either side, doesn't really matter) and wire that to the resistor pack's switched 12volt input wire(the thicker white one). Take apart the wire harness and wire in 4 separate positive wires to each injector clip, and those will go to each of the 4 resistor pack's output wires. Very simple.

13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)
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-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)