Carlo...this sort of noise was a problem brought up years ago (at least 10 or more ago) which afflicted cars fitted with DBA 5000 rotors (it used to happen on my '02 STi)....you can do a search, perhaps even on the DBA website. The issue came down to the anodising on the aluminium hats....from memory the solution was to clean off the anodising on the face of the hat where the wheel mounts up and also to clean the opposing face of the wheel....now I realise yours are PMU, but it may be worth a try....

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No Subarus currently owned