You are going to have to trace them back to the ecu/engine loom, i never found a diagram for the under dash plugs. Pick up a cheap multimeter with continuity tester to make it easier.
It looks to be a late model r32 gts-t loom (same as my old one) and the plugs have a combination of tach out, fuel pump trigger, water temp gauge, speed sensor input, all the consult outputs and a heap of other stuff i cant remember.
The other 2 plugs are mainly for the wipers from memory with a few other bits and pieces thrown in.
Somewhere in the 4 plugs there is the wiring for the dropping resistor for the fuel pump speed control, the output wire for the fuel pump speed, 2 wires for some water temp sensor for the climate control and a couple that run to the main power plug in the engine bay.