so whats been done to the car? mfi conversion? or is it a true mfi rst? iirc theres a wire that can get misplaced and cause it to overfuel on the ignition, as i think mfi has a start-up enrichment circuit, if thats not correctly fitted it will over fuel like a bastid, mate had a mk5 turbo and we changed everything when it was overfuelling, also started when you held the dizzy right over one end, would run for about 5-10 mins on the spot before the plugs fouled sounded like it was on three too.. i shall speak to him to find out what wire, basically tho he wired it up using a fiesta turbo diagram but a couple of wires are different

worth a shot, if not pm safechav he's real good with wiring probs