turbocharger oil leak and whistling at 1800 RPM

I have a Golf IV 1.9 TDI with 150 horsepower. During the oil change, it was noticed that there was a slight oil leak coming from the turbocharger. The average oil consumption is approximately 1 liter per 15,000 kilometers.

In addition, there is a hissing sound at 1,800 RPM, which is not excessively loud, but can be heard clearly when the window is open.

Can someone give me a tip?

Thank you in advance.

Hi,

Either the intercooler pipe or hose is cracked, or the connections of the pipes are leaking. O-rings in the connectors (haven't disassembled any yet)?

Best regards, Rainer.

Thank you.

As far as I know, no one else has tried that before.