@DannyP wrote: "weld a bung in. After you're done tuning, install a plug in the hole(use Neverseize)."
That's what I did for the O² sensor for my A/F gauge, which I just decided I don't need anymore. TOTALLY forgot that part about the Never-seize, though.
Like Jim, I get reminded of something cool (usually something I forgot) every time I visit this site!