There are two(or more) relays near the ecu connector, about 10-14" away, one of these is triggered by the ecu and outputs LIVE to the amal valve and fuel rail, as well as energising the fuel pump relay(when receiving a valid crank signal, or for PRIME).
Just to clarify the PULSED signal is NEGATIVE(earth) from the ECU, the relay supplies LIVE 12V to each injector all the time the ignition is switched on(position 2 or start).
DON'T get the two supplies at the injectors mixed up, just see which wire is the same colour on all four, this will be the LIVE from the relay.
tabetha