Yes,this is closed loop operation. The oxygen sensor is sending information to the computer and the computer is constantly adjusting the air fuel ratio based on the information it receives. If you have a chip programmed for closed loop idle,you will see the same fluctuation at idle. When you have open loop idle there is no correction so you will see a constant high O2 number at idle. You will also see a constant higher number at WOT because that is open loop operation as well, no correction.Is it normal for the o2 mvs to bounce around a lot under normal driving?