Proeagles, as I read your initial post you have four primaries that are tightly welded into the collector, and your O2 sensor is in one of the primaries just before it flows into the collector. Then you have a slip joint reducer that's over the collector, flowing into the exhaust pipe/muffler, is that right?

Jerry, can we let Proeagle answer this question, plus the questions in #9 before we jump into the "what if's" again? We need a better understanding of the system to engage in any discussion of substance, IMO.