This has been on my 12 a6 3.0t for a while. Replaced it 2k miles a go and has been performing fine.
diag; If car makes high pitch noise depended on rev while engine on lift the engine oil fill cap to lose vacuum, if noise gone as vacuum is leaking the PCV value is bad.
Fix; under super charger under fuel line(pressurized) on right side sitting mid way in the V with round plastic cover open the clips around the round cover and replace the valve and spring.