1.8 Turbo engine.

Hello everyone,
My very good friend has a 1.8 turbo that he might sell, before that I would like to know what kind of power can the engine handle (internals), what is stock boost and easiest way of boosting it higher, and whatkind of power can completely stock car handle with out upgrading anything.
I searched google but could not find this information.
Thank you for answering ahead of time.

I know people boosting 26psi with upgraded turbos and intercooler and chip ecu daily with no problems. Approx 280hp daily.