3g hemi gas mileage

Iam running factory computers. Factory Rams use 1 o2 before the cat and 1 o2 after, so since no cat you use only 1, thats the logic as it was explained to me when I got the harness. The only tuning I have done was a 91 octane, raised the rpm limit, and shift firmness. I took out the 91 octane after figuring out the mpg, but have left the rest, so its basically all stock computers, no aftermarket such as fast, mega squirt, accel etc.