Just got my new (to me of course) 07' G6 GT Sedan. I would realy like to increase the average mpg as much as possible. I know a good bit about cars but I also know that every car is different so I would like to know from you all G6 owners what kind of mpg increases you have calculated from various upgrades. I'm thinking about installing a CAI and new exhaust to get her breathing better and am figuring about a 2-4 mpg gain from this. 3-4 mpg is probably worth the $1000 to me but not 2. If anybody has other proven techniques, please advise.