Is the plug located in this diagram?
ecu pinouts for 1996 wrx: http://www.northursalia.com/modifica...ng/wiring.html
Some wiring diagrams from MY92-96, MY97-98, & MY99-00 Impreza turbos: http://www.jollygreenmonster.com/pinouts.htm
Hopefully you can trace the wires from the appropriate ecu pinouts and get the colors matched up with your female end of the engine harness. That's all I got. Good luck.