I am fairly new here and I am sure this isnt the first time the question has been asked, but I looking for ways to improve my milage on my 04 Silverado 2500 HD, 6.0 gas. Here are some of my low cost ideas: K&N air filter - how much improvement? tonneau cover - clean up the air flow, how much is it good for? 4.10 -> 3.73 gears - towing not a huge concern and wont affect it anyway. Also with the gear swap, do you change out the front axle as well? Its a push botton 4wheel drive system. This is the 1st 4x4 I have owned where I considered a gear swap. So if it sounds stupid, forgive me.