The tranny will out perform the engine any day. Thats assuming its stock. However if you are going to track i strongly suggest getting forged pistons, many of you are probably thinking well it doesn't need forged pistons unless he wants to make 500hp. Wrong the stock pistons used in our STI's are junk, ive had to replace a short block twice now because of broken ringlands, and im talking brand new factory shortblock, and no not a bad tune, stock motor, stock turbo. The composite metal pistons used are not sufficient. While your in there throw in ACL Racing bearings to eliminate the second most common failure. Throwing out a bearing, replace both main and rod its like $100 for the set.