Just got done doing some pretty decent mods to my '06 GT Auto last week(WMS CAI/SCT X CAL-2 with custom tunes from Brenspeed and 4.10 FRPP gears). Before the mods I was getting around 21-22 mpg running the 87 octane. Now after 2 tank fulls with the mods(93 octane tune as well) I'm getting right at 19 mpg. All my driving is a mix of 30 mile commute to and from work and city driving around home. After the gear install I try to keep my interstate speed to 70 tops(about 2600-2700 rpm in OD) to conserve some gas. I have yet to control the urges of getting on it pretty good from time to time now after the CAI/tune/gear mods, so I'm sure my mpg could pick up some...Oh well, it is to fun this way!!!!!