Jerry-
The o2 sensor is all a part of the dyno's computer. It WILL.........tell you if it's rich or lean !!!
It can give you so much information, the book is 3" thick. Suggest you read one and go over it with a computer/mechanic/dyno expert.
My intent is not to start a war over backyard tuning vs a dyno but, with today's technology, a dyno and it's computer is the best way of tuning any engine. Even on a engine dyno, it can tell you if you're lean or rich.