Just bought a new Honda Fit sport with a manual trans. EPA estimates are 29 combined but I'm seeing over 33 right now. I'm gonna have to drive a good bit more aggressively if I'm going to match those EPA numbers. I will do my best, though. My mantra is 'I am racing the dude in front of me. I will pass him. I will win.'
On a more serious note (F#), what would headers and a catback exhaust system do to my mileage?
They might require a tune to work long term. When the computer sees that the engine is running different than what it was told to expect, it might make adjustments until the output is at stock levels again.