Broken Wastegate? Noise 1999 Audi A4
 

We hear a buzzing/clicking noise (sounds like metal on metal vibration) when letting off the gas accompanied by low boost. Someone suggested it is the wastegate. It is flapping around causing the noise. I was told that you cannot just replace the wastegate. It is molded into the turbo so the whole turbo would need to be replaced.

Could that be?

Is there a way to test if the wastegate works properly (and the noise coming from something else)?

Thanks.

Volker