Sorry, should clarify incase you're not sure how it works? or for others..
All the settings on the SAFC at 0 = normal ECU tune.
A tuner will adjust these + or - a bit at certain rev ranges to get better air/fuel ratio's at those revs.
The ECU thinks it's sending AFRs to the engine components, but the SAFC intercepts those signals and adjusts them, and then sends them on. What a sneaky little russian eh?