AEM Cold(was long until the great flood of 2010 breaking #3 rod) H&R Racing did the re-hab. Kudos to Nick S. for such an outstanding job. Battery failure at two years and a back log of over 3 months forced retro. luckily there was room without the OEM air-box. All new braking hardware and Kumho Excsta AST 205/50's provide an excellent ride, 35-38mpg and handling that shouldn't exist in a go cart of this size. Would love to see the "SI" badging come to this model. Another 20%HP increase would be nice for those particularly windy days.