Sho, my man, you are going to have to calm down and start using some common sense. The T-67 is a _HUGE_ turbo that would require a ton of supporting mods. You aren't even at full understanding on basic bolt-ons yet, so please do not think about big turbo upgrades. Asking if that gigantic turbo would give "decent" power gains on an Evo is just absurd. Yes, that thing will triple your WHP if setup properly, but the cost of all the other mods you'd need would be exorbitant, plus it would be very risky for you to drive it around without having a lot of knowledge.
Don't worry about the fact that your buddy is selling it - just worry about getting your car setup and running properly while you learn all the basics. Later down the line, once you can recite the fundamentals of the Evo like poetry, then we can discuss turbo upgrade options.