Just from my experience with an o2 data logger, if you run it in the collector, it will read lean at idle and normal at WOT. As mentioned, put it in one of the tubes. I would use cylinder 5 or 7 just because they usually run the leanest. Unless you have a 5 7 swap camshaft. The other thing is I would call Holley, I don't think the O2 sensors tune much at WOT, they mainly are used for part throttle and cruising, that is where they learn and adjust the fuel maps. At WOT they are good for a data logging function.