""but am curious as to how reliable the source is.""

I tried to find it but I am pretty sure that a FAST rep showed the chart in another thread.
The chart is an interesting reference and now that thy are talking about E15, this would give us a good tuning reference if this takes place.

While trying to get to the magical 14.7 number, I have found that the engine wants what it wants. I know that I can not go any leaner on E10 than 15.8 on cruise, but after seeing this chart, I see why people are aiming for different numbers. I may shift my A/F range down from 14.5-15.5 max to 14.0-15.0 based on this chart. Or, not worry about my low 14 number during cruise thru out the temp changes of the year.