Has any testing been done on the wiring loom? The circuit is so simple it's not funny. Power one side of each injector, which is the same 12V source that supplies the ignitor; and a pulsing source to the other side from the ECU. Injectors No. 1 & 3 are paired together and so are No. 2 & 4(called batch-fire injection). The only components are the injectors, ECU and the 12V wiring source.