If it was built before 05/2002, it stands a chance the injector is gummed up with debris from the failure of the high pressure pump rollers. Remove the fuel filter and shake it. Collect the fuel in a clean container (preferably plastic). Pop a magnet under the container and see how many bits of metal you can collect. If the collected deposit is 10 mm diameter or more AND mainly black with some dispersed silver colored magnetic particles included, then roller cam, or shoe wear has taken place. If there aren't manybits, check for evidence of petrol or other contaminents. Bear in mind, any use of petrol will have contaminated the fuel system if not drained and flushed, so if petrols got into the injectors?? (if you get on with your local dealer ask them for a copy of TSB 042/2003)
The usual attempts by the dealer would be to re-program the injectors to the ECU firstly, then ship it to a Delphi specialist!