it greatly improved my top end... with the old style it would flatten out on the top, but with the new one the powerband is even smoother and the top end is now there. mike330r just changed his and he agrees that the top end is greatly improved. i did some measuring of teh 2 valves and the new one opens up 1/3 to 1/2 more then the older style. one thing mike and i noticed, or thought we noticed, is that we lost just a tad on the bottom, but not much