looking at Evo's. Few Questions.

[Kracka]

Nope, SST development has come a long way in the past few years, just make sure you have the latest revision ROM from Mitsu since the 2008 software was a bit buggy compared to the later releases. For a stock turbo car you're fine with just proper tuning and an aftermarket cooler. If you plan to upgrade your turbo then you should also plan on upgrading the clutch discs. SST maintenance will cost more than a GSR's 5-speed, but aftermarket fluid and filters are bringing that cost down to a more reasonable level.