Gregg what the turbo will do is lower your fuel rail pressure,in some trucks this will raise fuel mileage others lower it.The FASS system will take the air bubbles out of the fuel,and give you a better burn.Years a go a man in MO contacted me to try a system similar to the FASS,it may be same system.When you put your truck on a dyno,the shop uses the fuel out of their own system,its gravety fed to your motor,no air bubbles,the FASS is suppose to take the air out the fuel to burn the same way,so you get a better burn,therefore better fuel mileage.Thsi is what the guy from MO years ago explained to me.If you call Pitt Power,you will probably get the same answer