Been searching for this problem again today. Started with the same problem:



Number 3 overfueling..

I then changed the oil, dismantled the ISCV and totally cleaned it. Also checked the timing, ignition amplifier and the CPS when I saw this:



It was totally covered with a thick layer of oil en dirt. You can see I partial whipped it.
So cleaned the whole CPS, reconnected it and checked the gap. It's between 0.6-0.8mm, so perfect.

Than took it for a testdrive without the lambda sensor connected so the closed loop function wouldnt be activated. It ran beautifully!
After reconnecting the lambda sensor it still ran fine. So I think I finally have found the cause of this misfire in the dirty CPS!

Maybe the signal for 3 cylinders was just about ok, but the fourth one was too weak.. Could that be true?