headers affecting gas mileage?

I just bought some headers for my truck, and they are susposed to improve gas mileage. I was wondering if anyone has ever seen improvements in gas mileage because everyone has told me they always seen a decrease in gas mileage. This isn't why i'm buying the headers but I'm just curious.

any ideas?

The headers should help your gas mileage, and especially help your power. Anytime you improve the breathing of your engine, you see gains in power and fuel mileage.

You posted some RPOs and what they meant for rear ends the other day, and I was wondering if you had the RPOs for transmissions as well, and if you do, could ya post them? Thanks.

sorry I don't have them, I found them axle codes somewhere when I wasn't even looking for them but maybe you can find them in a search.