AFR and EGA question/clarification.....

[jjdalynh]

(i've been away for a bit and am just getting back into things, pls forgive the multiple posts)

i had read something in the past and reread it again this am and it still doesn't make sense to me.  there was an old thread on some other board that was talking about the differences between EGA tuning and AFR tuning with WB O2 sensors.    the statement was made that AFR is affected by the state of the combustion (efficiency, timing, etc) which confuses me.....   if you are using EGA, how does the efficiency and timing affect AFR?   unless you are saying AFR and Lambda are unrelated vs just being transforms of the other (per fuel type), how can Lambda be affected by the efficiency or timing if using EGA?   my understanding is that if you know the fuel type and the makeup of the atmosphere, if you are sampling HC O2 CO and CO2, then Lambda (and thus AFR), is the same regardless of whether your efficiency and timing is good or bad.
if the statement is just intended to mean "only using O2 sensors to read Lambda/AFR  then combustion efficiency and timing will affect the reading" then that's understood, i just want to understand whether i'm missing something.....