1994 Mazda MPV bypassing oxygen sensor

I am in the process of fitting a hydrogen/oxygen gas cell producer to supplement the petrol vapour. I have been told that I need to "fool" the computer so that it will not ADD aditional petrol vapour when I am feeding the supplementary gas to the intake manifold. Can I simply put a manually adjustable potentiometer across the two wires that used to feed the computer from the oxygen sensor. Set it for "rich" when cold then set it "lean" when warmed up? I would then leave the oxygen sensor disconnected.
Thanks.