Good point about the y-pipe. It is ridiculous. Crushes the pipes in half (picture).

At Guitar - when you are only getting 12mpg, that .8 is still almost a 7% improvement. I think the passenger unit bearing on mine might be crapping out anyway. outside of tire on that side is wearing....

There are o2 sensors after the cats. Remove them and it will throw codes. I am not convinced you will see a mileage increase either.

Header choice on the 2500s is pretty limited.