Pre and post turbo injection in an audi b5 s4

[rotrex]

I tried different jets. The noise is always there.
I'd not worry about it. It is likely fluid hitting the turbine casing wall at high speed.
I do not use pre-compressor injection in the moment. I use direct port injection.
Car is off the road until March. It's a roadster on UHP types and it is winter over here.