I have a Kohler Command Pro 25 on a Toro rider that is giving me fits! It was running poorly especially at higher rpms. I did a compression test and found a bad head gasket on one cyl.. I replaced it and it didnt help the performance much. I seems like when I get above half throttle it stumbles all over itself, i did a check on the spark advance module, and the ignition modules and they showed good. I flushed the fuel tank and cleaned out the carb.thinking maybe their was water in the fuel,but it didnt help. What am i missing? I still think it is a SAM problem but the repair manual test showed it to be ok. Is there anyone who has had this problem? Please help!