It's a Dashhawk II; it displays in AFR. Regardless if it was referenced for 14.7 or an E10 reference (which is what I assume you're referring to), 12.7 at WOT would still be perfectly safe. I have it set to gasoline, premium, which means no ethanol.
A datalog is only as good as the instrument you use and the sensor resolution it's getting its information from. So far so good on the old Dashhawk II in this application.
Ok, so your Dashhawk II is simply multiplying the lambda value from the OBD port x 14.7, giving you an AFR readout of 12.7. This equates to .86 lambda, which coincides closely with the factory values I posted earlier. And so my point is your Dashhawk interpreting the lambda of .86ish is nearly the same as my SCT reading .85 from the factory wideband. Your AFR value is actually about the same as my stock tune if you were to use 14.079 for stoich as the factory tune does. It is perfectly safe. Never meant anything otherwise. Now, if your 12.7 was referenced to 14.079 stoich, that would equate to .90 lambda, which I would consider unsafe for the factory E10 tune.
And back to the OP's request for dyno sheets showing AFRs...You'll find AFR values all over the place, just like the HP/Torque values from one dyno to the next. Because of placement of the sniffer and the stoich reference used to calculate the AFRs. I think it's better to monitor the values from the factory widebands vs a tailpipe sniffer.
Also, unless you did a WOT pull and immediately shut the car off to pull the plugs, your plug readings aren't necessarily from WOT mixtures. You're seeing the result of the computer trying to run stoich just about everywhere else but WOT, and this will make the plugs look like that. Finally...just my preference...I wouldn't pull plugs from an aluminum-headed engine while it's hot, risking galling the threads in the spark plug holes. I would just stick to reading the lambda values from the factory wideband O2 sensors.
As mentioned quite a bit, working in lambda is much easier than trying to convert the AFR readings. Then it doesn't matter which fuel you're using or referencing to.
2011 Mustang GT base, MT, 3.31 gears, E85 tuned, 47lb injectors, JBA stainless off-road h-pipe, GT500 axle-back, BMR springs, Roush UCA and billet LCA, CHE LCA relocation brackets, Strange 10-way struts/shocks, SPC aluminum adjustable panhard bar, BMR driveshaft loops, Barton shifter and bracket, JHR clutch line