We all used to tune for BSFC before O2 sensors became common.
Before that we tuned for EGT numbers.
At the proverbial end of the day - we should be reading plugs and tuning for the best number on HP/TQ
The other stuff is great for guidance - and O2 is better at predicting A/F, BSFC is better at determining efficiency, and EGT can tell you if a plug wire falls off...
