Tim, I added the GWR midpipe to my 2012 about 18 months ago, when I gfelt that the RSII muffler did not add the amount of sound that I was looking for. I was also looking for a little midrange torque boost as well. Even with the midpipe and muffler, the sound was not as loud as I wanted [needed
] so I have since performed a mufflerectomy and had a local shop weld up a Y-pipe and twin chrome tips in the rear. My car is now loud [to my liking].
As to the smog issue, California is [still] doing the tailpipe test, and who knows when they will finally convert to the OBDII-based testing, if ever. As such, the midpipe will impact the actual emissions, but by how much I couldn't say. Although the cat in the midpipe is no doubt effective, it is not OEM nor CARB approved. Emissions may be higher, but still pass. I guess I will find out in another 4 years.