AFR gauge with o2 sensor worth it or not?

I installed an AEM wideband HEGO with datalogging ($320) and boy did it help me dial in the part throttle on my blower car. I had it close on WOT but way too rich at cruise. It also has failsafes you can set if you lose fuel pressure. REALLY handy! After tuning I now get 11mpg and that is with two Demon 750 carbs, 4200 stall converter, NO overdrive and 4.11 gears with a spool.