I have a 1997 1.9 tdi Golf. It has been very good for ages but within the last few weeks it has started to make a noise that sounds like air being sucked into the manifold as soon as I reach 2000RPM. It does not do it when stationary and with the air box removed I can stall the engine by holding my hand over the air intake which would suggest that all the air tubes are in tact and there are no loose hoses. I have physically checked all the hoses and they seem fine. Could it be the waste gate on the turbo? Although there is no sign of power loss. The noise is loud enough to be heard over the running of the engine.
So come on all you techno boffins have a brain storm and please come up with something new for me to check. Thanx in advance. Gary P