Strange missfire/stutter

Hello I have an X reg Ford fiesta 1.25 Zetec. 2 days ago it developed a missfire when accelerating and also sounds like it has a small backfire occasionaly. 2 weeks ago it had a quick service new sparks new oil and filter and new air filter, I dont think the sparks or the HT leads are the problem as it has new HTs and new sparks and also when I take one HT lead off at a time the engine runs a lot rougher. I have checked as many sensors and cables as I can get to as I believed it could be the MAF sensor
, ICV etc. Out of the sensors I could get to, I was not sure what was what because haynes wasn't as helpful as it usualy is and am not sure if this model even has a MAF sensor as I have seen a few posts saying the zetec engine with the airfilter box on top of the engine block doesn't have one, I have ran injector cleaner through, put in different petrol to make sure it wasn't a bad batch and am now at a loss advise please anyone