I agree. I had one.
it lied. then the gauge quit working.
I got a complete replacement set, under warranty.
it too lied. then the gauge quit working.
I threw it on the wall of shame, and have never missed it and my plugs were replaced 22 years later with about 110,000 miles on them, NOT because they needed to be changed, but because I thought the car was sold, and so I gave it a tune-up. Buyer backed out.
My AFR may not be perfect, but by the plugs, I doubt an AFR could do better., Plus, you know, the car has, with one size smaller cam, and a lil more cylinder pressure, gotten UNBELIEVABLE (to some of the smartest guys here on FABO), fuel economy.
IMO;
RPM/Load/AFR/ and Ignition Timing, all go hand in hand. If you cannot change the timing on the fly, Nor change the AFR on the fly, as is the case with a carburetor; what's the point of monitoring the AFR?
I mean, that's like watching your wife gain weight, and thinking you can talk to her about it. If yur stupid enough to try, as I was, stand well back, and be prepared to rough it for a week or a lifetime.
Just let her/it, be, Cuz just like my wife goes around complaining about how fat she is, that AFR will do the same.