We have a 2002 S60 Volvo(not turbo charged) that makes a whistling(sucking)noise on 2002 Volvo S60

We have seen a fix for a turbo charged Volvo, but this car is not turbo charged. The other fix was for the PCV valve. Please help

Asked by for the 2002 Volvo S60
Vacuum leak someplace. Have it smoked or mechanic check it.