Sound like a dribbling injector, Quick, cheap fix, buy some Diesel injector cleaner. Warm the engine to running temp 90 degs approx. Add a small amount of cleaner, neat into to the Fuel filter. Drive the car hard, for atleast 10-15 Mins to clear the system you should see black smoke in your rear view. This should be a quick/cheap fix, if not more expensive intrusive maintenance required.
Another Nigel C
January 2010