[Crash68]

Turbo "farting" is just part of a Variable Geomertry Turbo operation. A VGT has vanes that control the boost pressure, when let off the suddenly while building a lot of boost you'll get it. Blow off valves are not needed with a VGT as they just serve to relieve excess boost pressure when the throttle closes suddenly.
A new 6.7 Cummins will do the same "farting", it's just harder to hear over the engine.

nope, probably no way to make it sound better, it's just trying to spin backwards at 50-60k rpm

the turbo doesn't spin backwards, just the excess air pressure forcing it's way back across the compressor wheel.