My understanding is that the V-Tune started with STi Docklands trying to make the WRX more driveable day to day. Vinny eventually moved to the Liberty 3.0's (which a few GenIV 3.0's have done on other forums), and after popular demand, recently started doing the GT's.
From what I've read and researched from other people's posts, gains is supposed to be from 10 - 15 kw. Like Chris said, it's mainly to make it more driveable, and not meant for large number gains. After all, it is performed by someone officially working for Subaru, so they need to keep it conservative so as to not void any warranties.
But cost is where I'm getting conflicting reports. The WRX people claim it's only $350 for the V-Tune. But some of the Liberty owners I know who called up got quoted $800. I'm guessing because of the volume done on the WRX explains it's lower costs?
