Numbers are kind of hard to guess in this case because I don't know what type of dyno you're going to be on. The Mustang Dyno's in this area put a stock STI at ~220whp. A stage 1 (stock + tune) makes about 240-250whp and a catted stage 2 like your car generally makes around 260-270whp. Now remember that this is on california 91 octane and a low reading dyno. For dynoje numbers multiply by 1.15 and you should be in the ballpark. Good luck and let us know how the tune turns out.