Not to be argumentive, CK, but, to each his own. Until I have a chance to check on the performance of the Zinger Pro,(performance in my opinion equates to mph), all I can do is relate to what I myself have witnessed. On a regular 22X8 Zinger my engine turned 6900 rpms. When I switched to the Zinger Pro, it ran 7400, same as you claimed. I'm reasonably sure there was an improvement, just how much, can't be judged standing on the ground. I will find out this summer.