MODs for better towing and mpgs on 07 silverado

Wondering what I can do to increase HP and MPGs on my 07 Z71. Really dont want to do anything that will void my factory warranty (anyone used the GM catback exhaust or air intake)? If I get the Superchip Programmer will it void the warranty even if you set it back to stock hen you take it to the dealership?

If you have bigger tires than stock you could upgrade the gearing, then you wouldn't have to touch the motor, on something that new I wouldn't mess with your motor too much, any changes from intake, exhaust are going to be minimal and you won't really notice it, throw some 35s on there with 4.56 gears, it will tow like it has 600hp....or a diesel

why woudl you reccomend bigger tires for better mpg/power? Yes, regearing may help it feel more powerful, but it will do teh opposite to your mileage.

I'd get a decent bolt on intake, get a decent exhaust system built, and leave it at that.

I was just thinking to regear with stock tire sizemay not be that beneficial and you may overgear it killing your top end, but if he were to eventually put on bigger tires he could overgear it then instead of regearing just a little with the stock tires, MPG is screwed no matter what you do, I know exhaust and intake companies claim better mileage but when you're towing its screwed anyways, just my .02c