What boost would a T28 turbo hybrid by Turbo Technics (360° bearing)fully rebuilt run been told you can only run 20psi max is this about right

Have a t3 fitted at the moment but want to put a smaller turbo back on as rouse cars had.

I got 320bhp at the moment but don`t really want to loose power would a T28 hybrid 360° bearing give me the same BHP as a normal T3