Johnny... What you just said sparked my interest but I'm a little confused. I have a flowmaster 50 series with dual exhaust (very free flowing). I also have a superchip and run premium. My gas mileage stayed the same as stock around town, about 16, but when I took a 600 mile trip on the highway it stayed at 16. I was expecting to get into the 20's. Please explain that EGR thing and what I can do to increase mileage and/or get better performance.