Have you actually used a multimeter at the injector connector to see if there is power to the injector? A test light (WTF is a noid light?) like I think you were talking about isn't going to tell you much of anything, you need a real diagnostic tool like a basic multimeter. You should see the same thing on all four injectors. If you don't you have a fatigued wire (likely on the power side) or a bad injector driver (ECU side) in the ECU most likely. Most of the time the injector has power on one side of the coil (an injector is a type of solenoid) and the ECU completes the circuit to ground to turn the injector on. So if you have power to the injector, it's safe to say that you have a problem on the ECU side of the fence, with wiring or the ECU itself, etc.

Someone who knows how to use a multimeter can narrow down the possibilities in a few minutes or less.