| Hey welcome to the site!
The motor itself is a big motor. Mine unloaded gets 13 around town. I just towed 10,000 this weekend and it averaged 10mpg. So regularly your gonna use more fuel than your 5.3. Any exhaust will help especially if you loose your catalitic converter, I used a 4inch MBRP with mine then eliminated the muffler. When I towed the 10k it haule fine with no drown at all. The programmers are all more or less the same. I like hypertech because of the cost and design. Make sure if you get a programmer not to add over 85hp or you'll risk burning the tranny.
With towing, everyone drives different . I baby mine and dont mash the throttle to the floor when going up hills to get more power. If your like me then you will loose power but if you dont care and go like hell you'll tear ass up the hill but burn the tranny and turbo or motor in a few thousand miles.
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