A/F/R gauge for tuning

Yes possible.
Something I see with the help of Egt's for each cylinder is somtimes there is a wide spread between cylinders. These motors can be hard to tune. Lean the richest cylinder and now the leanest cylinder is unhappy and vice versa. Moving the o2 sensor could have just made the fussy cylinder or cylinders happy. With only one sensor sampling an average of 4 cylinders the fuel injection has no way of knowing how those cylinders are running individually let alone the four on the other side that aren't even being sampled.