I have noticed something different about my ST205, when under boost (especially between 3000rpm and 4000rpm) I can hear fluctuations in intake noise. It sounds like this: "pssshhhssssshhhhssssshhhhsssshhhh". Is it normal?
I have CT20b in my ST165, but it is very steady (although I got 2 externals, and the turbo is steel, not ceramic like in my ST205).