Air Fuel Ratio Meter ????

[4RnrRick]

Who here is using or seen one of those Air / Fuel Ratio Meters to determine how "perfect" your engine is running? Do these really work? What brand and is it worth the $$$? Do you have some type of POT switch wired in so you can tweak the mixture on the fly? How do you like it?

I'm wanting to "fine tune" my 85 22RE so I can get the most bang for the buck out of my current mods.
85 22RE rebuild about 8000 miles ago, X-Large 5" K&N Cone Filter #RU-2800, 3" diameter intake tube, 94 Throttle Body and Upper Intake Plenum Conversion, Plenum, EFI Runners, Intake & Exhaust Ports ported and polished, DOA C270 EFI Cam, LC Adjustable Timing Gear, Head Rebuilt with OEM Valves, Cylinders bored 0.020 over, 2 1/4" Doug Thorley Tri-Y header, 2 1/4" exhaust from header back, No Cat and EGR