I am having trouble with my Kawi on my Super Z. At low and mid RPM everything is great. When I get into the upper RPM's, the mower tends to stumble a little. It sputters and almost acts like it wants to die. This has been happening for a week. Any suggestions? I am going right now on the idea that it is water in the gas. Also, will you be able to get a 27HP Kawi this year or just the Kohler?