AFR guage

Ironmike said
I want one just for tuning purposes. I guess I'm looking for one that will just show me "real time" AFR, whether it be idling, cruising or WOT.
I sure don't need something that's a pain in the *** to work, or something to obsess over. It seems like with today's gasoline, it's just too hard to look at a plug and know you're good.

I'm putting out pretty good HP and an extended lean condition could be a disaster.

I think you'll know that before the gage tells you - except perhaps at the track.
Part thottle, cruise and idle some engines can go quite lean, and how lean will vary from engine to engine. At light to moderate load too lean they shut off or rev and shut off.

If you're already somewhat familiar with plug reading, there's some guys here that can help you with reading - even with todays street fuels. eg @yellow rose