I am a newbe here. I have an 08 chevy cc with the 6.0. My question is has anybody tried or is currently using some of those after market air units that supposedly increase the gas milage. EX The Tornado. I wonder if they work or will increase the gas millage as stated. Also I have noticed that durning the winter months I seem to get worse gas millage. Is this due to the colder air or ? I have been told a tuner will help but I am affraid of what it might due to my warrenty if GM finds out.