2.0 TDI turbo "air leak" noise

Hi, I have 2.0 TDI BMM engine that recently started making a very distinct rushing air noise on press of accelerator particularly going uphill. On lower load there is almost no noise - such as revving in neutral or cruising at motorway speeds.

It is not the siren noise of broken turbo, but nonetheless my friend who is looking after the car could not find any broken pipes by doing some primitive inspection and suggested it could be bad turbo. I'm not convinced yet and want to make sure before spending that sort of money.

One other thing the exhaust is not in a great shape and is missing a cat.

I have VCDS and can see no fault codes yet.

Where should I start looking to identify the leak or confirm bad turbo if they can actually cause the air noise? Thanks.

That's smart, bad turbo is the last thing you want. Rule out stuff.
Did friend remove lower engine cover and look from underneath.
Missing catalytic converter is no problem, but loose or open exhaust could be.
I suppose a leaking vacuum pump could make that noise.

Yes, he did look underneath. The exhaust does sound a bit like a straight pipe for some reason.

Strangely enough today the weather is warmer (9c Vs 0 last few days) and the air noise is now barely there. Could there be temperature correlation somehow?

Check/inspect the EGR cooler closely. Any signs of soot around there?

If you have access to an air compressor you can test for leaks

- remove air intake hose.
- attach plastic bag to that end. Use hose clamps and tighten enough for sealing taking care not to distort plastic hose.
- remove head pcv into air intake.
- use an air compressor hose with a level acruated tip. Use a clean rag aroind it amnd insert the air tip onto the pcv hose of the intake.
- blow air at a reduced psi enough for the plastic bag to inflate.
Have a helper listen for leaks around the air charge piping. Might need to crawl under the car.
- if your plastic bag stays inflated a fraction of a second you close the air level on the compressor source you are most likely ok.
- if it never gets fully then you have a leak

Good luck