None of these modifications will make any noticeable difference. The folks who designed your truck have already maxed out the gas mileage, and if any of these tactics made a difference, they would already be done from the factory. That V10 does sound nice with a free flowing muffler, though, which means you probably shouldn’t do anything like that. I once installed a straight piped dual exhaust system on an F250 4X4 with a V10, and the owner reported that his mileage went down to 7 mpg, entirely because he couldn’t keep his foot out of it and loved that sound.