I have an Audi a3 2.0 TDI 2007. Was driving when the power of the car suddenly went down in power. It still drove but power was exceptionally less. It feels like a turbo has gone and is not as responsive or fast as before. Only slightly but still a noticeable difference.
Driving down motorway/highway at 50 mph when it suddenly lost power. Would not reach 60 mph however hard I pressed the gas pedal. I switched the car off and back on and it seemed ok, although power from engine is now noticeably less than before and just takes time to accelerate with power. The revs are a little higher too than before from 1500rpm to 2500/3000rpm when changing gears. Could this be the air flow meter that needs replacing?
Have the engine control module checked for fault codes stored. If that doesn't point you in the right direction check the fuel pressure while driving, I replaced a fuel pump on one of these recently for the same problem