207 1,4 Hdi High Speed Sound Problem

Hello friends 2010 mofrl 207 1,4 hdi starts a high speed in my car, between 4000 and 4500. This sound starts to sound like air sound, it stops when I take my foot out of the gas, it starts again when I press it again. I showed the hope of the turbocharger in Ankara, the vehicle said that there was no problem with the turbo but there was an air leak somewhere. Where do you think this kacak could be

Actions at the Authorized Service
Tried with zero turbo
Manifold checked
Air doser checked and tested with a new one

But there was no sound, they couldn't find where it came from. If anyone has an idea, I would be very happy. The warranty of the vehicle continues.

If the vehicle has a guarantee, I think they do not mess with themselves