You can add them to most GIL, Stainless marine, imco, etc, style manifolds. In the riser. I can however, see it being a issue with lightning headers.

in the origional post he stated [cmi big tubes] so i assumed they were dry,as most are,my ss welder can put o2 bungs in your header and it will in no way ruin your headers,he does it all the time.as allready stated,reading plugs is not an acurate way to tune a marine engine[dont ask me how i know that]o2 sensers reading air=fuel ratio is the most accurate,and the best way to tune,period.