Well.... Most CAI's are less restrictive and flow air better than the stock filter/airbox, so in theory you should see better gas mileage. Whether it's enough of a difference for you to actually see it at the gas pump though is doubtful. Most people who add a CAI to their 03/04 Cobra see a big REDUCTION in gas mileage though.... This is because they can't keep their foot out of it listening to the louder blower whine!!!