I have a vectra c with z22yh engine, beleive it or not I am having some fuel issues. White smoke, strong smell of fuel, mis firing and undrivable but it occasionally clears and runs fine. I beleive I should have a constant voltage to the injectors and the othe side switched to ground. If I'm right, my first question is what voltage should I have? secondly should this be ignition on or engine running or both. And finaly to clarify this is to battery negative?

Yes that is correct and the earth pulses the injector
Cannot remember exact voltage but think (distant memory) that it is battery voltage (12 volts upwards)