Have lost oil pressure 3 times now
1)2133cc vw type 1, 1/8th mile track, blew the #3 cyl out the side of the case, snapped the crank in 2, and the cam in 3 places...all due to a broken oil pump gear keyway. NO gauge, no way to know, suspect I snapped the keyway on the warmup/burnout.
2)427CI GM big block, pulling a run, 1/2 way down the track lost all pressure, shut it down, saved the $15,000 motor. Secondary oil filter line failed.
3)Laguna Seca, 84 Honda on a track day, zero pressure registered, shut down, saved motor, oil cooler line failed
My point was, there really is no reason to have a A/F guage if you are not protecting all the other far more important things. If the A/F goes off a little, you are more than likely not going to eat a motor...oil pressure goes, and your screwed.
I would just hate to see new guys getting into tuning, to think a A/F is all you need and ignore the important lifeblood of a motor.