Yes, I have that AEM in your link with the Bosch 4.9 sensor setup to plug in anytime I want to see the AF ratio. The gauge is mounted in a temporary mount with a switch to keep it off most of the time. I got the special clamp to hold the sensor into the rear exhaust pipe with the cable running through my trunk, out the soft-top case, and between the seats up to the gauge so I can turn it on and see it when driving. When not in use, most of the time, I just coil it up in a plastic bag in the trunk (It gets pretty dirty with carbon).
I had envisioned mounting it to the exhaust manifold permanently, near the engine, but doubt I'll bother now that things are running so well and I can plug it in to get data easily if needed. The sensor is very sensitive to moisture which will damage it quickly so you don't want to power it on until exhaust has reached full temp and you are positive all the water vapor is out. I dont even mount it and turn on unless the engine is fully warmed up. I killed the first sensor by cold starting with it still hanging off the exhaust. ~$40. This probably wouldnt happen if it was mounted near the engine and heated up quickly...which is why you see them pretty close to the engine on modern cars.
I've learned a lot about how the engine runs under different conditions. Early on it was useful just to quickly confirm if too rich or too lean, especially when the starting systems were not adjusted very well and I was messing with all the shims. I had been pulling the plugs pretty often but it takes time to adjust, run long enough, and then pull the plugs again to look. This eventually damaged the threads on one which I ended up time-certing and as well as that repair worked I'd like to delay doing more of them. Timecerts are great quality, very durable, but tedious to install with the head mounted.
I think with a generally well tuned engine I question if AF data is required since the linkage tour and idle adjustment procedures work well, at least for fine tuning at hot idle. Recently I've just used a vacuum gauge mounted next to the WRD to assess small timing adjustments and I suppose its not surprising to see highest vacuum correlate with ideal timing and mixture. Vacuum gauge can also tell you a lot of other important things about the health of the valves at idle, but also at various loads at speed.
However, I think AF will come in handy again when I want to check the FIP adjustments at higher RPM and under load. Other's on the site have done more work with it at speed vs. load and I think and its worth getting some of their feedback on how well that has gone and if it was reliable enough to make FIP adjustments. Eventually I'm hoping to use it to understand if improvement can be made at higher RPM at cruising speed to optimize milage.
Up till now, after making any adjustments on anything, I've made sure to check AF at high speed to make very sure its not running too lean, which can cause serious damage. I figure its safer to be a bit rich at high RPM, live with a little lower milage and not risk burning anything up because of a bad adjustment. Also feels like it makes more power on the rich side, ~13 vs above 14 but thats not proven, it might just sound better to me. If the FIP and linkages are adjusted to spec I dont think you can get in too much trouble but AF gives some confidence.
