A/F/R gauge for tuning

They read averages and i think it's a few hundred readings per minute but i'm not sure. The better ones read all 5 gases and when used on modern engines they can record and provide many tuning options and curves. I have twice been saved by mine which exhibited a flooded condition once and a fuel starving issue another time.They show exactly why it's hard to clean up the idle with a long duration cam. Without one you have a calculated guess at best but guys with a lot of experience can get pretty close without one...but not me. I have mine jetted and tuned to 12.0 - 12.5 at WOT, 13.5 - 14.5 at idle and 14.0 - 14.7 at cruz. Again these are averages. On our carbureted classics they only provide A/F ratio.