Weird noise N55 engine

[SilentBob81]

Hi everyone,

my name is Alex, I'm from Stuttgart/Germany and I seem to have a "unique" noise coming from my N55 engine because wherever I tried so far nobody seems to have an idea, so I hope anyone here may have experience with it.

I will attach a soundfile of it, hope it works...it may also be found here:
https://vocaroo.com/i/s1r0ecubiXlH

It occurs at idle and happens once every few seconds mostly when the engine isn't properly warmed up yet.

My dealer already wanted to change the turbo, as he thinks the "turbo wheel" may be scratching at the housing. However to my understanding the source is somewhere around cyl 4-5 from top of the cylinder head (injection, ...?).

Would be great if anyone had an idea, I'd like to fix whatever is behind before severe damage occurs...

Thanks a lot and best regards,
Alex