Simlar to SR20, about 10-20kW (maybe more, maybe less) with a tune and a happy dyno.
Earthing the factory boost solenoid will get you 8psi, or replace the waste gate with an RB20 one (10psi).
Look in the RB25 dyno thread, lots of options and results there.
You should be more focused on the drive rather than dyno numbers.