I thought along the same way about dividing the flow of gases in two and so it dosen't really matter if 02 sensor is sensing flow from six or just three cylinders provided that burn is the same on all. But what about that pesky air ijection pump that must make a hell of a difference.
I'm also not sure how installing sensor in the H pipe would obstruct its proper functioning ?
Help me out guys with some of this exhaust theory <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Good judgement comes from a lot of experience and a lot of that comes from Bad judgement

3.4L 91' Trooper
4.3 TBI, Airmax 1" TB spacer