The S-AFC works by intercepting the MAF/MAP signals to the ecu, so I can't monitor A/F ratios by that means, correct? So, I will have to take an egt reading from the O2 sensor (is that possible by means of an OBD2 scan tool?)
it kinda depends on the software you have. With the type I have (Which I think is Harrison), it's only good for an instantaneous reading...which would be worthless to try to tune. However, with the other type (i can't remember the name), it can read everything in real-time, and then you can tune.
For reference sake, the "sweet spot" for the O2 reading, is about 0.78 V.