Grimspeed

do you have an aftermarket turbo intake? Sometimes you can get a flutter through those intakes especially if its a cheap one. Sounds very similar to what I had in my old gc8

possible that your turbo is running out of flow causing the gate to close then open ect.

pay money put it on a dyno.

Yeh I don't mind putting it on the dyno the only problem is the closest dyno is 600km away so was hoping to try sorting it out before gettin to the dyno.
Na no aftermarket intake.
Running a td06-20g at 1.1 bar so it shouldn't be running out

You need to bite the bullet and take it to your tuner.
Pinging sounds like gravel rattling round in a tin can so I doubt it's that.
Could be compressor surge. Is it at WOT? Or more at part throttle?

It only happens at wot about approx 4000 and after the external gate has already opened. Is there any way to identify if it is compressor surge. Boost seems to be solid even during the sound