VW TDI Tip
Provided here is a tip from Volkswagen regarding all models equipped with the TDI engine that exhibits a low-power complaint.
Check the mass air flow (MAF) sensor reading in the measuring block, group 00, field 10. The value should reach 255 under full load.
If the reading is low, check the air filter and air box for restrictions. If the filter and box are OK, suspect the MAF is at fault.