with those mods like a custom catback exhaust or muffler...and K/N filter intake whatever...you actually get worse mileage because more power = more gas. i previously thought that it woudl be better mileage but turns out not really and i asked a friend and he told me that it's a myth...so yea...fuel goes byebye. i only get good mileage doing highway driving...other than that i get nothing. maybe im wrong and i just drive really hard since i got my custom cat and intake....

~~BEST MOD = rip out all the interior and if youre fat, shed some pounds and then maybe the intake and exhaust will shed 1/2 - 1 second off ...maybe more! and run 16 inch rims or hubcaps so lighten the load even more if you want quick pick up speed. YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA taht's the way to gooooooooooooooooooooo!