What to use other than lamda?

Can I tune and use the same equation as target lambda divided by current lambda then take that and multiple it by the previous value of the kpa at the rpm I am adjusting? So if I have a target of say 14.1 and my afr reads 13.1 I divide 14.1 by 13.1 then take that and multiple it by the value it was at, for that rpm and kpa? Hope that made sense..

Hello yes that is correct you can do that