Some supported serial widebands send the AFR value to FlashScan, some send Lambda and some send both. Some allow the stoich value to be pre-set in the wide band controller for different fuels some don't. It is too difficult to support all the different combinations of wide bands by allowing FlashScan to set the stoich value. To get the correct AFR that you want/need for different fuels, I recommend creating a calcualted PID based off of the serial lambda value.
Regards
Paul