[TruckbusUK]

Listened to your clips again, and at first thought ... noisy injector, then the engine revved, and mmmm still think its a belt that's too tight or on its way out or maybe a pulley that's moving on its shaft, but if you say its coming from the other side of the engine, maybe noisy injector is right.

Can you see the pulley faces? ... if its a belt and is breaking up it will mark the pulley groove "v" much more than other pulleys the engine has ...

Intriguing ..interested to hear what the root cause is.