Could be the injectors which are gunged up or partially blocked depends on the milege its done! Also check fuel all fuel lines from filter are unblocked Also have u replaced the fuel filter you are supposed to renew every 12 months due to rust and condensation build up in the tank,you should try using the drain plug at the bottom of the filter to see if its just diesel thats coming out use a clear glass to catch it in and let it settle, Back to the injectors, Have you ever had them cleaned or replaced each injector usually costs anything from 20 pounds each to 35 pounds each, Also a note that i recently came across a transit with a similar problem due to the fuel lines corroded and letting in air so its maybe worth you checking as well to see if this is the case as well for you!
Ian Mechanic, April 2009
