I am adjusting a LS2 based tune for my LS3/480. In checking various values i noticed a number of LS3 tunes have a O2 base mv (bank 1 and 2) of 650mv. Accordingly the lean/rich range adjusts accordingly. The 650 value i got from a recent ls3 tune recommended here on one of the forums for the ls3/480. I always thought for the narrowband 02 sensors the set point for stoich was 450....which is what my ls2 has. Why the difference 650/vs450. I see a number of ls3 tunes with a 650mv base. Not sure what i should use. Is this a difference of cat/vs non cat? I am running headers with no cat.