[TurboKraft]

This GT30R question comes up frequently.

Simply put, the turbine wheel is too small for a 3.3L engine, and a little big for most built up air-cooled 911 twin turbos. It is a good turbo for 3.0L Turbos, though.

If your power goals are very modest, and you have stock cams -- great. Your engine probably doesn't flow much anyway and you won't find the turbine side restrictive in the camshafts' limited rpm band.

If you have the usual 930 upgrades -- headers, muffler, intercooler, boost, cams -- then the turbine is a limiter. Ex: a 3.6 Turbo with EFI that should have done an easy 520whp on pump gas at 1bar was limited to 480hp, and had much less midrange torque, thanks to the existing GT30-based turbo the client didn't want to change.

Backpressure.
It is your enemy.