1.8 zetec that i used tp have in my mk4 escort and was beautiful the whole tim eit was in there, took it out and put it into my fiesta si as the head was warped on the si, was running fine (never drove it though as it was staying at work) only probelm with it was that it seemed to be overfueling a great deal and when i removed the cat when putting the engine in a lot of it well erm fell out so to speak!
so in light of it overfueling i figured ok im still running the 1.6 lambda sensor il swap it for the 1.8 one i had in the escort. did this and it didnt really seem to change much. but as the engine got hotter it started to missfire when reved untill unless you really gently pushed down on the throttle really slowly it would just cough and splutter then cut out.
im thinking possible blocked fuel filter, as the demand for fuel will increase a lot quicker if just bliping the throttle sharply rather than really slowly and progresivly raising the revs.

also came across a plug that i cant for the life of me remember where it went!
car is running external EDIS. if you follow the crank sensor wires they take you up to a larger multiplug and the mystery plug is the only other plug thats in the loom up to the multiplug to then connect to the EDIS module.
anyone got any ideas?