Since I can change the AFR of my motor on a whim quite easily, I have played a lot with my motor. My motor definitiely starts to choke on more than about 12, and by 10 ti's flat falling on it's face. 13.5 is ideal I thinkhigh twelves to about 13.8.

Other factors play into things that will make it challenge to get WOT perfect across all the RPM ranges. For anythign other than WOT 13.5 to 16 isvery runnable for crusing and very light throttle. I run as lean as 17-18 for long highway stints at cruise, but that's how I get 18MPH from a ~600 horsie motor.

Greg