By increasing the amount of exhaust that flows out of the piston (job of the header), is an exhaust header making the car use up more fuel by allowing more fuel to be taken into the piston upon intake?

Thanks

 

Your fuel consumption will probably go up a bit only because with the header you'll tend to "give it" a little more.

 

There are some people that will tell you they get better gas mileage. Whether better or worst, it will be very very minimal and probably not even noticable. If it is a good design it should net you better gas mileage since you lower the exhaust restriction a bit, but not to much to lose the backpressure the engine needs. They are normally a few pounds lighter than cast iron ones as well. However, they are louders, so like mentioned above, you will probably lose the mileage due to the ill effect of stepping on it more.

 

hypothetically you should get better gas mileage... like they said though, you prolly won't cause you'll be pushing it a little harder