zetecs suffer from plugs leads and air flow meters, n they all give that kind of effect, but if you've had plugs and leads try unplugging your air flow meter, it will go to a base setting, so it should run OK with it unplugged if its faulty! my old xr3i 130ps was the same, unplugged air flow meter plug and it was fine just a bit fuely! then bought another off ebay for a 10er! but in the worst case it could be a valve burning out or head gone pourous!?.... try AFM first tho its free 2 try lol.