I've seen an O2 sensor that 'fools' the computer into thinking O2 is fine..and doesn't need replaced. Anyone had any experience with these, are they worth the money? If so, I see no need for an actual O2 sensor..

I believe some fashion of exhaust gas monitoring is required for fuel injection systems. I watched speedtv install of EFI on a 65 chevy and one was installed that came with the kit. Whats the point since O2 sensors are so cheap anyway?

All this does is sends the correct voltage to the ECM which tells the ECM that the car'* exhaust is normal. Problem with this is, that if it'* NOT normal (IE EGR Problems, etc) The ECM may never know it & your car can run like **** & it will be near impossible to diagnos because of this device.

Exactly. Without the O2, you may never get an indication of another failure. Running too lean or too rich can be caused by other sensors. The 02 is your last line of defense.

Also the O2 simulators only show 1 signal like a real O2 sensor. So the computer will be confused and they are really only meant for off-road use when you are at WOT most of the time since the computer ignores the O2 sensores at WOT.