I sent an email to Greddy to ask if I could use my AEM Uego on their Ultimate Emanage (it was not listed as an option) and they replied this:

"The reason the AEM unit is not listed as an option is due to the fact that the AEM unit graphs differently than a unit that graphs a linear 5 volt curve. If you would like to hook it up you need to put in conversion values and this will give you an accurate range from 10.2 to 12.5 A/F. Anything outside that range will be off the further you get away from that area. I do have the available conversion chart that I can fax if you have a number I can send it to. Thanks for the email."

The AEM does have a 5v output so what are they talking about?

 

My guess is that the AEM does not provide a LINEAR 5V output.

This would explain why it would be accurate in the stated range, but would that it would be off more and more as you get out of that range.