[Badbubba]

Yes, all depends on the fuel. Need to know the stoich. Then you can determine your afr. It's easier to deal in lambda. Program your stoich into your wide band. Then .85 lambda would be about the correct value at wot N/A 12.5 afr for a stoich of 14.7, which is gas with no ethenol. .85 x 14.7 = 12.495 afr. For FI, a wot .78 lambda would yield about a 11.5 afr. .78 x 14.7 = 11.446 afr.
For E10, gas with 10% ethenol, stoich is about 14.2. Program the wide band for 14.2. So, a lambda of .85 would be .85 x 14.2 = 12.07 afr. .78 x 14.2 = 11.076 afr. So, if you deal in lambda, it doesn't change, but the afr will change depending upon fuel.
If the wide band is solely programmed for 14.7 stoich, then subtract .5 from your afr for E10. Like dan stated.
These are the numbers I shoot for, .85 (E10: 12.0afr) N/A wot and .78 (E10: 11.0afr) spraying.

Also, just got this in the mail yday. Just add tap water and the gas you want to test. The ethenol absorbs the water. Then read the percentage of ethenol at the separation line, between the ethenol/water mix and the gas. Pumps in the area state upto 10% ethenol. Tester indicates 10%.