2.0 TFSI (CDNC) strange engine noise

Hello friends,
I'm encountering really weird sound on my 2012 facelift A5. It actually happens only, when engine is cold (after startup). I've been to 2 workshops already, but they did not find the problem - since it happens only under certain circumstances, it's hard to diagnose.

It happens if following conditions are met:

• Engine has to be cold
• Engine speed has to be in range 1000-1800 RPM (approx.)
• Engine needs to be under slight load (does not happen with clutch pressed/neutral and also does not happen with heavy load)

The sound itself is hard to describe - it’s low tone - humming/grinding sound. I made a quick audio of it (recorded about 2 meters from the car). It was recorded right after the cold start. I was slowly driving off from standstill to slight slope.

Link (headphones recommended): https://soundcloud.com/kamil-ture-ek%2F20-tfsi-noise
The sound is hard to pinpoint. It's audible from the whole engine compartment (maybe a little bit more audible from the turbo area), and it definitely comes from intake also (when i get closer to intake port, it's really loud).

Important thing to note is, the car is running perfect. It does not consume practically any oil and it drives really well. VCDS does not show any faults, workshop also tested the compression and it's around 11,5 Bar (+- 0,2) on all of the cylinders. So engine seems to be in really good health (apart from the weird sound ).

I'll be grateful for any ideas/thoughts what might be the cause, or how could I proceed with diagnosing. I'm really desperate, because as I wrote: nobody wants to waste time with such sporadic fault I suppose.

Thank you.

Kamil