O2 (nb) use?

[classicauto]

Well honestly not 100% sure on what the Rtek would do, but likely its use of closed loop is no more in depth then the stock ECU. So by losing the 02 sensor you're only going to lose the closed loop function - which is only going to be on in light cruising anyway. And since you can tune out those areas in the Rtek, you should be able to make them as smooth and fuel efficient (if not more so) then what the closed loop will do anyways.