I had a short and an rechecking the wiring. The wiring of this diagram doesnt agree with the WRX ECU. I just measured current on each of the partially pink injector wires and all of them have a (+) signal, while your green wire states that it requires a (-) signal from the injector.
http://www.innovatemotorsports.com/r...ru_Impreza.php
This shows the same thing.
So is the polarity OK? Because I'm pretty sure most of the WRX if not all Impreza have a common ground and only "speed" (+) outputs to the ECU from their Injectors.