Okay, Here Goes
I've seen wiring schematics for circuits that are supposed to simulate the signal from the O2 that is after the catalytic converter. Now of course these say don't use for the O2 sensor before the catalytic converter. Now I understand the reason for not using this device in front of the cat because then you would have an absolute constant air to fuel ration and who knows what it would be. However, if one were to make the device variable (i.e tuneable) would could tune their air to fuel ratio as they wanted. Of course there would be the danger of over leaning and doing engine damage. But still it's an interesting idea.
I'd be interested to here others comments or thoughts.