Right bank leaner than left

We recently acquired a mustang dyno, tech came out to show how to use new holeshot software, while running the power pulls we started to watch afr through the dyno, we have 3 engines we are focusing on in this question and the dyno tech couldn’t answer for us. There is 2 small blocks one carbureted and one efi and then 1 big block carbureted all 3 are running great pulling low to mid 8 seconds on the 1/8 mile track between 235 hp and 345, while On the dyno we found that afr of the right bank to be off as far as .4 to 1.0 in afr. The numbers follow each other when accelerating but the right bank always stays leaner than the left, all three do have other than stock cams, and tuning 3 different size exhausts, we have tried swapping sensors and right bank stays leaner at all times, it does appear to be more noticeable when warmer. Is this something to be concerned about or? All 3 are not using any pcv valves just open air crank ventilation

OK, so swapping the sensors didn't show a change. What happens if you swap the wideband controller (ie, you plug the one for the left bank into the right bank sensor). Does the bank difference follow the wiring -- now is the left bank (now labeled right bank) is leaner. If so, then it's the wideband controller, or the dyno calibration for one of those channels that is off.

Swap injectors between banks (all left injectors swapped with all right injectors) and see if lean bank follows.

I've had an intermittend misfire due to bad ground on a LS v8. Didn't pick up the misfire, but noticed a lean running bank. (Lean, because no combustion =O2). Fixed bad ground and that was it. Took me a while to figure out though.. lean = not enough fuel right? wrong, was no burning of fuel in this case.