99 taco V6 only running on 5

weI know the exact problem but dont know whats causing it

Cylinder number 2 is not firing due to its injector we know this for fact

But here is the kicker. When it cold starts it runs on six we checked the fuel injector it is working then if u cut it off and cut it back on in a few mins it works fine but if you let it sit for 20 or more between that time and when it is able to do another cold start it will only run on five causing a horrible shake and no power the fuel injector is not working then and if u punch the gas when it is running on 5 the check engine flashes meaning gas in the exhaust we put a new rear o2 sensor, sparks plugs, fuel filter and cleaned the mass air flow tand the throttle body so far. It has the same amount of spark when on 5 cylinders as it does ion 6

PLEASE HELP!!