That noise is very distinct, they should be able to isolate that relatively easily.
I’d suggest having someone rev the engine to induce the noise while you observe the wastegates. If the noise coincides with the movement of a wastegate, then the linkage or actuator is at fault.
I’d suggest having someone rev the engine to induce the noise while you observe the wastegates. If the noise coincides with the movement of a wastegate, then the linkage or actuator is at fault.