Just bought a 1999 Imprezza WRX,

Was fine for a while but now finding a wierd whine sound happening when im trying to maintain speed in any gear not accelerating or decelerating. The boost gauge has between 15 and 10 psi Vaccum at this time.

Could the be a problem with the turbo or does anyone know what this would be

 

Faulty wheel bearing perhaps? Can you roughly tell where the noise is coming from?

 

15psi is 1bar so doubt your getting that in vaccum? And 1bar boost is not cruising,its standard max boost on wrx
Have you checked pipes for splits/holes?

 

Cant hear where its coming from and my boost gauge says 9 psi max when accelerating but drops to 20 vaccum when idle/decelerating

 

At 9psi/0.6bar you're not getting full boost. Check pipe work as 1st port of call