Hoping someone can give me a clue...
I have got a 2004 A3 2.0 TDI and am getting a strange, high pitched squeal from what sounds like the turbo, the noise only occurs at low revs (i.e. about 1500-1800) and only on flat ground i.e. if I apply more pressure to the throttle the noise shuts up pretty much instantly or if I am going up hill and the engine is having to work a bit harder the noise does not occur. Also, the noise doesnt kick in until about 20 mins after starting from cold.
Someone told me that it may be the 'veins' or 'valves' in the turbo that are clogged up and are sticking at low pressure which kind of makes sense as like I say when you apply more pressure to the throttle the noise disappears. The perfomance of the car doesn't seem to be affected as the car pulls well in all circs.
I suspect (but hope not) the turbo may need replacing, but if anyone has experienced the same or has any suggestions as to what the problem might be I would appreciate your input.