Air fuel gauge ,info
 

Trying to find the right setup. Wanting to only monitor a/f for tuning . Some will monitor a run or so by recording for playback. Then some only real time. Lots of them on the market.
Anyone have info on these? Not looking for expensive data recorders that monitor everything. Just to tune and possibly record a run.
Fast has one that seems to do just that. But what all is needed ? Thanks.