Modify O2 sensors

[GasSavers_brick]

What does lean burn really do, anyway? I keep hearing that it doesn't help a "normal" engine but I can't figure out why. Reduces power, forces driver to open throttle more, reduced pumping losses while cruising for increased efficiency? That's all I can think of since you theoretically reduce power output in step with the leaning effect.

If you really mean business, I would source wideband O2 sensor and develop a hack box that translates between that and your stock ECU. You set the target voltage range on the wideband that correlates to your desired A/F ratio, then the box monitors the wideband and generates the right high/low outputs so that the engine thinks it's around stoich but it is actually doing what you want. To do anything with the stock o2 sensor is just a rough and only semi-controlled approximation of lean burn. The best system would allow you to switch manually between stoichiometric and your desired A/F ratio in case things get too hot, or better yet monitor the ECT itself and switch over automatically if things get out of hand.