I have a '91 z28 5.7 and replaced the intake manifold gasket, in doing so had to unplug the injectors from the pigtails. Now that it's all back together I'm not sure if a couple of them are on the right inj. cuz of a small shake from the engine at idle and low speeds.

 

it doesn't make a difference which pigtail goes to which injector. they all share the same ground.

 

Each batch of injectors(driver and passenger) shares its own ground which is produced by the ECM. One of the pins on all of the injectors is set to a possitive 12 or so volts(not sure of the exact value). The other pin to is for the computer signal. The injectors opens when the signal from the computer is low(ground) and closes when the signal is high(possitive) just as the wiring diagram shows.

 

What they are trying to say is that it doesnt matter what plug goes to what injector....just plug them in. As far as the small shake check for a vac leak....hose....bad gasket. Also be sure to reset the ignition timing and make sure you have the plug order correct.