And keep in mind that the o2 sensor in the exhaust or in each exhaust is reading the overall composite of all the cyclinders fed to that exhaust. If an individual cylinder is a bit leaner or richer, you won't see it from a common o2 sensor. So, that is aonther thing to keep in mind when tuning with an o2 sensor; you can think you are doing great but in reality, 1 or 2 cylinders are getting a bit too lean, with no margin. (And I bet SOMEONE has put o2 senors in each exhaust tube!)
As said, don't let the AF meter do all your thinking......
