This is a issue I had when first attempting a 25:1 + A/F. I ended building a lean burn hole in my fuel map with my desired 30:1 in the middle and a leaner value on the outer perimeter to keep the engine from hunting to get out of the lean burn hole. One other thing I found out is I could only build one preset light load lean burn value in the map, because of the space it would take up.
My heavy load 10 to 14psi would run at 20:1 A/F with no knock on pump 91 octane.
Here is a pic of a light load 53 mph 30:1 A/F. The A/F shows 18:1 because this is a AEM wide band and the max value is 18:1. The mass air an fuel show around a 30:1 A/F ratio. This screen shot is a earlier version with out my pre heat intake setup and EGR enable. I'm now running as much as 2psi at this same mph.
