Possibly, due to the known flaw in these turbos. Bearing wear can cause the whistle and result in turbo failure in time.
If you can take the inlet pipe off the turbo and with your fingers carefully check the turbo wheel for play. Wiggle the 'axle' seen in the pic below. If it moves more than a mm in any direction then a replacement turbo would be prudent. Sorry if some of that you knew already! :smile:
If you do want to go for a replacement turbo can I recommend a hybrid 727477 unit from Turbo Technics. Hopefully everything is fine for you though

. PM me if you'd like details on the turbo. I've recently bought one myself and it's an excellent unit and will be much stronger than the standard Garrett item.