Well after a week with the muffler and filter my mileage has increased. Im now getting 14-15 in the city and 20-21 on the highway. That is just normal driving, 65 on the highway and regular city driving (not slow, not fast). I am very happy with the results of these two mods. The sound and performance is great and I highly recomend it to anyone looking for an upgrade to the stock hemi.