Im currently running a GT-40 upper and lower intake,and I saw this upper plenum in Jegs,for use with the GT-40 lower.Its called the max box,and it says its good for 20 rear wheel horsepower.Does anybody know about these before i blow 450 bucks on one.
Usually the box style uppers are designed more for high RPM applications. It really depends on the rest of your set-up as to whether or not it is worth buying. I can just about guarantee that you won't get 20 at the wheels from it though. The GT40 upper is a damn good upper, and you are probably better off keeping it.