You should have an earth from the ecu to the fuel pump relay (on my gts4 it was in the boot not sure if it's the same) to switch it when running. It's easy enough to just use a new relay to rule out bad wiring plus up rate it a bit. Using the ecu signal to pin 85,battery positive to pin 30 and 86,then 87 is your positive to your fuel pump then just make sure you have a good earth for the fuel pump.