Sorry I didn't check back before installing it just a couple hours ago. I'll jack up the car tomorrow night and get an OD measurement at each end.
I took some sound measurements with my phone before and after (with the back seat down) and there was a 4 or 5 peak dB decrease in normal driving. I still got almost the same dB level at WOT, especially towards the top of the rev range, but that may be more due to the supercharger than the exhaust. I may still want to quiet the car down some more, but boy was this a huge improvement! Now there is no risk of getting 'blatty' even at larger throttle inputs. It used to be almost impossible to not let the car sound too loud in my neighborhood, but now I can just drive normally and things don't get out of hand.
Below are a couple before/after in-car videos.