boost leak or something worse?

okay I have a 97 eclipse gs-t, stock motor except for greddy turbo piping kit,bov, and intercooler(stock turbo). my cel is on, I had the code read and it is maufacturer controlled fuel and air or something, not helpful. anyway the problem is this. the car runs like it is not boosting although the gauge shows normal boost levels. When the turbo spools up it makes a loud squealing sound(not compressor surge, already had that) and the car falls on its face, loses power like its gonna die until I let off. I cant tell if the sound is air escaping like a boost leak or if its something squealing. can anyone help? before this problem the car had plenty of power and now it feels like an n/a eclipse even before the squealing and stalling starts.