Thanks for coming to Just Answer to ask a question.
Do this. Spray that belt with a little water during the time its makeing the noise and see if it changes the sound of the noise if it does not then I believe the belt is not the source but a intercooler leak or intercooler hose leak or a concern with the turbo fins being sooted up and not adjusting by way of the solenoid. This would cause the turbo to make to much boost and whistle. Also look for exhaust leaks from the manifolds at the heads or rear of the turbo or after the turbo.