Okay here was my test rig, i went to the junkyard and got a main relay connector, plugged that into the main relay, on the other end I crimped spade connectors and inserted those into the cars main relay plug.
I started the car and reved the engine up to about 4,000rpm and then disconnected one wire at a time. Every wire except the blue will shut the car off. Some of them will just shut the fuel pump off and the engine will continue to run and slowly sputter to a stop.
Any wire that instantly shut the car off also shuts off the fuel pump. I checked by having my digital multi meter connected to the fuel pump, and when you would disconnect a wire like the black ground wire, the engine shut off and there was no voltage to the fuel pump.
I wanted to disconnect the power wire that feeds each injector, except I did not feel like hacking into my engine wire harness. Someday maybe i'll do that, but for now i'm going to do the relay switch.
SO, I totally agree that putting the switch on the ground wire is the best idea. Hopefully somebody that is curious if the fuel pump gets shut off will benefit from my testing.