My tune uses the O2 feedback below boost so I need both banks monitored. From the hundreds of logs I have collected, if you are using an aftermarket ems you need both banks monitored and controlled with O2 feedback. The corrections to my fuel map are different from bank to bank esp at different rpms. In my car the rear bank is more efficient around 3900-4300 (than the front) and the O2 feedback adds fuel to that bank but subtracts a small amount to my front bank. Everywhere else my feedback subtracts a small amount of fuel in both banks but at different rates to keep it around 14.7.
At WOT I run on the fuel table and both banks are pretty even (11.3) ----- even in that 3900-4300 range.
My new tune from SoS is 420rwhp 317rwtq and I avg 28mpg on my trip back to Vegas. That's with short gears and the 4.235 R&P.