Intermitent whistle during boost (B8)
 

Hello folks,
I am pretty desperate with the whistly noise coming from my Audi Q5 2.0t 2013.
It is pretty audible in the attached video below but to describe it in words the whistle appears during the boost when it reaches higher PSI or the boost threshold. It is an intermittent whistle similar to boiling old school kettle. This is only happening when engine is loaded and with revs between 2000-3200 rpm ( I guess that is pretty much a boost range).

I had 1st turbocharger installed in May 2021 and since the whistle was there. The original turbocharger had pretty worn wastegate so it wasn't really boosting and possibly that is why I haven't heard anything at that time.
Anyway, I had the car in two shops and last one "Audi specialists" have recommended replacing the turbo again.
So this time I have decided I will swap the turbo myself but after putting everything together the exact same whistling is happening -> I am positive on the fact it is not the turbocharger itself neither the DV as it always came in new with a turbocharger assembly.
Try to solve this I read the PCV/oil separator could be the issue but I have just installed the brand new one and the intermittent whistle is still there.

When the car was last time in shop it was tested for boost leaks and there were found None.
Turbo is OEM K03.


I am out of ideas and pretty frustrated with what could be causing this given trying to fix this for the last 6 months and spending at least $3000 to get the turbo working fine not even counting my time I have spent on it.
If there is anyone who has any ideas on how to further diagnose/ fix this, please let me know.

Did you ever work out what the issue was? I have a 2009 A4 2.0t Quattro with the same noise from 2500Rpm - around about 3000.
I've tried Diverter valve, PCV, N75 but cant for the life of me work this on out.

I still have that whistle. Since that I had it in shop as my engine got busted and had to do timing chain, tensioner, some new lifters and whole thing was resealed. I talk to this old dude in shop and he said it sounds like intake. I have to say that it is currently not that loud as it used to, I also got some better air filter in. I am suspecting there might be some hole somewhere in the airbox or some intake pipe tear. My Q5 was in collision on that side in past before I purchased it so maybe there is some tear somewhere.

If you ever manage to solve it please post your solution.

Check your oil dip stick cap whether it seals. Not sure if it is related but I found mine a bit popped out and when I pushed it down I can still hear it but I feel it is less audible now. There might be a bad seal potentially.

anyone has a though about what the whistling could be or have same issue??