I just added a pair of AFR guages to my g-2. It is "interesting" to compare the readings for each rotor. It is also "interesting" to actually see what afr is doing while at varying power points on a track.
That said I agree with Chris that unless you have sophisticated and very $$$ fuel/ignition controls your ability to correct any particular problem is pretty limited.
At the ARRC this year my motor just would'nt pull. The AFR meters clearly showed that the secondaries were'nt comming in as needed. (it's a long story about "improving" stuff that works just fine)
I R&Red the secondaries and all was well again. The meters made the diagnosis simple. (then I ran out of gas after starting 59th and working up to 10th or 11th. It's a real drag to watch all the folks you just passed whiz by while you're stumbling around!)
I personally like the AFR guages and will use them for more tuning as I become enlightened to Mazda FI.
TT