Your correct the engine would not run at all with pipes mixed up, I refer to my first write up your running on the 5th injector only....hence bursts into life...but only on the fuel from the 5th, do Test there is a 12v supply to Pin 1 on ECU, also while there check Pin 2 is earth..ie..negative, 2 esentual circuits for ECU, BUT before doing above check the "Coolent Temp sensor" yellow plug, under the intake manifold is fully secure..no broken wires / clean connection, as this is the only way the ECU knows to increase pressure to all 4 injectors via the pressure Actuator, if all perfect make sure the Pressure actuator located on the metering head towards the front, that the 2 pin plug is secure / clean. There is a Full Test hear that I can explain, but one must have good knowledge of use of multimeter and ohms testing.