Ok, so next we have done 1 7/8" headers into 2 1/2" HF cats, we also did the 160 degree tstat and tune. This has added 44.9 rwhp to my car. Which if you have been following my build now puts me at + 101.9 added rwhp. Pretty good for just these mods i would say. Now, the interesting thing is when we did the base dyno before the headers they put my car at 646 bhp. Which is crazy with just an Araid and a tune. I didnt believe the numbers, so i brought my wife 2013 Black A6 ZL1 over there and had them do a baseline run on it because it is still all stock, and thier #s they got from hers corrected out at 581 bhp. So they are pretty much right on. Here are some pics of the dyno sheets before and after the install. I will post the pics, vid of install if Mark over at Speed Sports, in Gilbert, Az. recorded it like I asked him to. I also included to vids one with me revving the engine in neutral standing behind it, and another of me coming and passing by the camera with a high rpm shift into second.