annoyingrob

Yes and no. The ECU manipulates the duty cycle of the injectors (aka, how long the spray lasts) to control how much fuel is injected into the cylinders, that part is absolutely correct, BUT the ECU can't just say "Hey, I'm going to inject 10cc of fuel".

The ECU's fuel map (Think of an excel table with engine speed on one axis, and air velocity on another with each cell being the resulting duty cycle or pulse time) is pre-programmed at the factory to match a cpecific size of injector. If the table says that the injector needs to be on for 20ms for a certain speed and a certain amount of air going into the motor, the injector is fired on for 20ms. That time period corresponds to a specific amount of fuel on stock injectors at a specific fuel pressure, at a specific voltage. If you increase the injector size, the engine will still fire the injector for the same 20ms, but will end up injecting MORE fuel due to the increased size of the injector.

The ONLY time that this can changed is during closed-loop mode. This happens only at idle and constant speed situations, the ECU will read the O2 sensor, and will tweak the amount of fuel it's delivering to the engine to match a stoicheometric ratio. There's a limit to this though, the ECU can only tweak the pre-defined map so much, and those changes are temporary, and they don't happen all the time.

Running low impedance injectors off of an ECU that expects high impedance injectors with a resistor pack will work perfectly fine. The Supra guys do it all the time. 1JZ-GTE motors run high impedance 390cc injectors, and a popular upgrade for them is 2JZ-GTE 550cc injectors (low impedance).

The resistor pack on the turbo trucks is a metal brick near the intake manifold with 3 wires going to it, but any large wattage resistors around 5 ohms (I think, I need to verify that impedance) will work.