well i broke this one in ..and it fu***n rolls...im on 110 octane with a 50:1 ratio...and it was rader at 57 mph..out the box....damn good craftmanship...i just odered a 17mm carb stock is a 12mm..carbon fiber reed vavles and a thinner head gasket to close the squinch area down..and i lil nos kit off ebay.....u gota know what your buyin in thease things..i had one from pep boys it was ok to cruzie on but thats it.....big diffrende in the one from pep boys and the one i have now..also big diff in price