On the 05' (B) motor 5.3L we did not make any real power over stock on the towing tune.
It is going to have better throttle sensitivity and better shifting on this level. A better tune for you may be the stock with options tune. On this tune you can run the lower octane fuel (87) and still have the better shifting and throttle feel.
Neither one of these tunes are going to help in mileage while towing.
Making adjustments to the trans options or govenors will not help in fuel mileage.
All of the trans options are based on half throttle or more, part throttle transmission shifts are going to stay closer to a stock point.
I recommend to start off using the preset trans tuning for the towing, and then make adjustments based on your driving habits.
Do you tow in O/D? This is not good for the transmission to keep shifting in and out of gear.
I personally do not use the O/D when towing, under 65mph or when the torque converter is not fully locked.
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