Well they are meant to get louder but not in the way you mention.
What are you going to do? Reco it? These turbos can be rebuilt, but not hi-flowed or upgraded. That turbo can do 1.1bar. Don't go over that. If you blow it, you gotta buy another one, because once you blow them, they can't be rebuilt. This is what I was told by a turbo house.
Let me know if you need someone who can do it or need a price?