zetec's tend to eat plugs and leads,also coil packs tend to go down from time to time
also check lambda sensor is working properly had this go down once made it stutter.
also get the tps checked (throttle postion sensor).
also should get the maf unit on the air box checked to see if running properly,there is a way to test this unit simpley remove the air box when running and blow into the maf should make the car run lumpy,if it does nothing its faulty get a new one not second hand
hope this little list helps to emlimate a few things good lucky m8