When I did that, it basically just made the car louder. IM not sure for your car (since mine is so much older) but it was so insanely quiet. So I went to the local exhaust shop and they replaced the lunchbox with a straight pipe and put a tip on it for cheap. I didnt really notice any gains. Maybe +1 or so mpg. But in combination with a header, I noticed a huge difference. I am now getting 35 mpg easily and noticed an increase in acceleration a bit.
Hatch Nation #92 || FocusXtreme #13 || Zetec Crew #377 || Rally Revolution #4
September 2014 ROTM