I run the banks and gained 1mpg roughly if I keep my foot out the throttle. First week I noticed a decrease but that's because I was getting on it pretty good to hear her "sing" have your driving habits changed or maybe the type of driving, like streets vs highway? Give it a few hundred miles for the comp to adjust to the extra air flow maybe? Otherwise I would just recheck the install and call banks techs for any troubleshooting tips.