i had poor preformance from my 1.9 tdi mk2 2k,the power was ok up to 2000 rpm but after it was flat i unplugged the maf sensor and it was worse,so being a tight arse i took the sensor out,(oh yes fords have fitted a hex bolt with a round stud in the center good pipe grips will get around this)dipped the sensor in white spirit and with a soft brush lightly cleaned out, a few tiny bits of dirt came out, blew it dry and refitted, amazing the car has never gone so well and i have had it for nearly two years, its worth a try if you break it you gonna buy a new one anyway