two very common faults with the 2.0tdi is the air flow meter or the vacumn system, throughout the engine there are various rubber vacumn hoses, these tend to split at the ends resuting in lost pressure. these hoses can be checked by a pressure tester one hose at a time, the vacumn pump could be faulty also.
putting the car on the computor will point you in the right direction.
pedlow
December 2010