i bought some aftermarket injector pigtails (the clips with the wires on them) and i dont know which wire i should hook up to the injector resistor box for my MPFI swap..i searched...but since the two wires on these plugs are idenctical...which one is it?

 

If you look at the plug from the side where injector plugs in, and turn it such a way that the half-round cut-out is facing up, then it's the right pin (wires are behind, that's why I'm naming pins instead). Than pin goes to resistor box.

 

If you have the pigtails you will see that each injector plug has one wire that is the same color on every plug. I believe the wire is RED. That one goes to the injector resistor box.