This is how I made my adapter when experimenting with High Impedance Injectors on an '86 GXL:

The Ballast Resistors for the Low Impedance injectors are in the rectangular aluminum can on the front of the RHS fender...you can see the plug to them just in front on the first picture. In the second picture all the wires on a spare plug are all wired and soldered together and an insulated electrical connector used to cap them off. Using this method I could easily swap back to the low impedance injectors when my experiments were done.

 

I double checked the FSM and it works exactly as you said. 1 wire goes in (power from the Main Relay), gets split four ways, each goes through a resistor and then hits their individual injectors. It's the same on Japan-spec 86-88 cars as well.

The only thing I could suggest as an improvement to your jumper pack would be to toss the wire nut in favor of either a crimp connector or soldered joint, and given some double wall heat shrink to keep moisture/dirt/whatever out. The last thing you want happening during injector experiments is for the power to the injectors getting funky at WOT. It's a good way to blow an engine.

Want to hear a joke?
Engine: Knock Knock?
Owner: Who's there?
Engine: Rebuild!

 

He soldered, just the hokey wire nut and tape are misleading.

 

High impedance, modern style injectors that don't suck?

To take advantage of course, you'll need a standalone to drive them, which makes the resistor pack and/or bypass obsolete.