Hi I have a 1.9td Seat Alhambra on a 2003 Plate. It has developed a mis fire when up to temperature. It sounds like running on 3 Cylinders but only when warm, its fine for first 5 miles approx. I have read lots of possible issues just wondered if anyone could give me some advise. I havereplaced the Fue Filer and also put a Fuel System Cleaner through the system. It appears worse under load for example at take off and up hills. Thanks in advance for your help.