Can k04 wastegate go broke?
2 - Using VAG-COM or ECUx log the requested boost pressure and actual boost pressure. If requested is significantly higher than actual, you are losing boost.
3 - Hook up a MityVac or some other sort of pressure hand pump. Connect it to your wastegate lines. Wastegate actuator arm should just start to move at about 7 psi.
Catalysator blocked? Crack at turbo?
I think, that this has to be something, which appears only a bit higher boost and gets air to bounce between turbos.
Did you pull codes? If codes dont tell you anything, pressure test, change plugs, change coils, and see if that helps.



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