I'm guessing this is in response to my reply on your thread.when you run them inline one behind the other in the flow path of the exhaust you cause eddys and vortices that stop a lot of flow around and over the following sensor and can have them surrounded by a pocket of stagnant air.they should be clocked around the pipe from each other like 1/3 of a turn apart or spaced a deceint distance apart along the pipe.
Ok, I haven't seen anyone relocate the narrow band to the dp. I have seen the wideband in the header before. Not a great idea, but it worked for a while.