How due you know when the ecu went back to stock settings, does the s-afc setting show 0 or still the programed settings. Also how long does it take for the ecu to reset, And if the ecu resets will it still work in open loop mode at wide open throttle.
You use the dyno to adjust air/fuel mixture to get better HP but you have a base run to start off with. A few weeks later if you go back to Dyno to dyno your car and find your numbers are similar to your base run dyno numbers you would know it got resetted.
Its not the cheap way to tell, but atleast you are not lying to yourself thinking that its still working.