You're sure it's the turbo? I had a power steering pump make what I would call a whine before. I think anything belt driven could have a problem like that at the pulley. If the turbo had an imperfection on the shaft it could squeal, in which case, it could be that. How are you on mileage? You may want to take it to the dealer in the case that it's the turbo. I wouldn't want to eat that cost on a car under warranty. They sometimes will, depending on the dealership, try to say that modifications were the cause of the failure (i.e. you put on a high flowing open downpipe which caused the car to spool the turbo more than it was designed to). Just be aware of that sort of stuff. Can you take a video of the sound or at least an audio clip? That always is beneficial in narrowing down sounds. Or if you can be really descriptive, like saying it sounds like finger nails down a chalkboard amplified 10 times. Sounds like really helps if you can't get an audio clip. Also, you can YouTube stuff and see what pulls up and see if anyone else has posted your issue before.