[wagonman76]

I built an O2 modifier circuit from a document floating around called D17.pdf. I tried it in both cars (the Celeb and an 89 6000 with 2.8) and no matter what I did, mileage went down a little when leaning a little, and went down a lot when leaning a lot. Perhaps it would be better suited for applications when part of the gas is being replaced with something else. It also seems that the inline battery method might be a better idea.