I have the same problem with my car, although mine also stutters. I have a 2001 focus 1.6 Zetec se Automatic. If i drive mine steady to 50 mph my revs will sit at just over 2k if i put my foot down only half way it will splutter and jump like mad with very little speed increase. also with an auto i can kick down a gear if i do this on the odd occasion it will kick down the revs will increase to say 4 - 5k but no increase in speed what so ever. I have just had in the last couple of weeks, a full new exhaust, oil filter change, new plugs plus ht leads, air filter, fuel filter drained and flushed coolant and refilled as the car also overheats if i am doing say 80 down the motorway take my foot of the gas it will over heat then or after a few minutes but goes back down to normal temp pretty quickly aslo had the Lamba sensor think thats right changed in the exhaust. none of this solved any of the problems but have no found a split in what i think is the PCV pipe would this be a cause of my troubles? hopefully ill get one tomorrow?