Weird sound on deceleration

[andrew2k]

Hello!
Recently, I came across a problem : when I accelerate, on deceleration there is a strange sound, but I'm not sure whether it comes from the engine bay or from the exhaust area.
I have a recording with the sound below, the phone was sitting on the floor next to the final exhaust.
Engine is OM651 on a B200 from 2015.
You can easily hear the sound , but there must be silence for the sound to be heared.
Google drive link with the sound:
https://drive.google.com/file/d/1o7FECKP5WKvBkGPHBLXpY9QkNHLg6CgI/view?usp=drivesdk

Couldn't upload it here because of file extension restriction.
Thanks for the help!

 

[ajlsl600]

Temp block exhaust tailpipedetermine if u have a leak up near manifold or turbo area

 

[andrew2k]

And how do I find out ?
The engine will be out of the car while changing timing chain, so the mechanics should find out if something is wrong ?
Also, the car has DPF OFF (diesel particulate filter is off), maybe this is the reason? (I've been told so by several mechanics.