About 10-15 HP. You may want to consider the Throttle body bypass mod to get the all the free mods out of the way. Hooker Long tube headers and Mufflex Y-pipe will net you about 40 HP gain. The Hypertech is a big waste of money, it works well in stock 4th gens, but actually loses power if the car is modded in any way. Also a valve cover breather will do nothing, just spit oil all over the top of your valve cover, use the stock routing to the throttle body. Also an air foil does nothing, save your $40 and apply it towards a 52mm TB down the road when you get headers installed. | 
