The bike can and does run without imput from the oxygen sensor. Its purpose is to "sniff" exhaust and relay info back to the ECU so that fuel flow can be adjusted back to 14.7 when the bike is in closed loop (relying on its pre programmed maps.) http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=48 Its range is limited, hence called a narrow band oxygen sensor. Twist the throttle and the bike goes to open mode and uses the other sensors on the bike to arrive at the proper A/F for the conditions. All the oxygen sensor and subsequently the ECU knows, is that the exhaust is outside the scope of measurement. It is all book learning on my part, but leads me to believe the A/F ratio under those circumstances are pre programed too, based on what those sensors are monitoring. In a dyno run, the bike is in open mode. Am I correct in my assumption that it is the signal downstream from the ECU that gets the adjustment?, that would be the only way to capture data from the 3 remaining sensors. An oxygen sensor would seem important on a dyno run to arrive at proper settings, yet you rarely see them posted. It still seems a coarse way to capture all the real world options. I believe the Auto Tune comes with a wide band sensor. The oxygen sensor detects exhaust deviations the stock sensors cannot. Seems to me that is pretty crucial, as it can make adjustments to account for wear and changes in injector flow rates, such as partial blockage. Depending on the adjustments, it is possible all readings would be outside the range of a stock sensor. My beef with the stock ECU is that transition from 17 to 1 at warm idle to something usable when the engine spools up. At cold idle it will be something richer. I assume a Dynojet mod, will be richer yet. Maybe some one with more knowledge on what/how a Dynojet is adjusting, would convince me there is no downside to it.