So I recently got a p0300 random misfire code and I've already done the following:

-Changed (new) 6 ngk spark plugs
-Changed (new) 6 ignition coils
-New Throttle body
-New Valve cover with new PCV valve


I have check for vacuum leaks and everything is fine. The car idles really rough and it wont stay on if I dont steadily hold the gas pedal down a little to keep it from dying. There's definitely a misfire since I get a bunch of popping and violent shaking.

I also get a bit of dark black smoke when I rev it up to 5-6k which indicates unburned fuel.

All 6 plugs are completely black at the tip and still look new at the threads but they are wet, which I assume is from unburned fuel



I would think the Z1 motorsports Fuel Injector sub harness might be the fix, any ideas of what else it could possibly be?

 

Injector stuck open?

Why not diagnose it properly instead of throwing parts at it?

I haven't tried it, but I'm pretty sure it would run on 5 cylinders without it stalling.