Helo everyone, yet back with a weird problem sound.

Engine is as above code crlb 129k miles, no dtc, no issues but a weird sound as per following link:

2.0 tdi unknown sound 2 - YouTube

No clue what it is and cause of for last 1500 miles since noticed. Do to it and that was do soon on the car :

* Cambelt with water pump
* Glow plugs( as one was playing up
* Cambelt again without water pump thinking might be related causing the sound.
* Aux belt and tensioner also suspected as i had a spare kit.

I usee a stethoscope to try to pin point it and the loudest it can be heard from injector 4 feed pipe.

Any opinions?