my brother has a 93 300ex that sputters when shifted into 5th gear. it never does it at any other gear or rpm. it has good gas in it, the choke is NOT on either. i cleaned the carb, put another carb on it, changed the cdi box, cleaned air filter, changed coil, plug, and the little box on the left side of the front between the cdi and the coil, i am not sure what it is though. changed gas tank and made sure all vents and gas line was open. oh also it is stock jetting, and all the parts that were changed was off another 93 300ex that is in good running condition and still runs good with all those parts on it that were swithed. does anyone have any idea where to go from here? sorry this is so long.