Multij

Hey Guys, I have a problem with my 93' GT Turbo, it is misfiring and basically the car is permanently working on 3 cylinders and running very rich, compression is good, we replaced injectors, high tension leads, plugs, checked harness, and the problem still persists. When unplugging the injector plug that is on the fuel rail on this particular cylinder the idle does not seem to waver, but on the others it does. Did anyone encounter this problem? Maybe someone can shed some light? Thanks.