I found that with the JCW airbox that there was not much sound at all unless you had the stereo off and the window down. With this setup and driving normally it is a bit louder (only just hear it over the stereo) but not annoying at all. Put the foot down and allow the turbo to boost up and it becomes a different story. Sounds a lot more like a turbo sports car and more what I think a turbo mini should sound. Kind of makes it up to me that the supercharger whine is gone.
As for the silver piece near the elbow, it is all 3". Yes I know the stock pipe is 2.75" but it does fit just a bit tight. I will eventually change out the stock pipe section once I have a new one fabricated (probably a polished aluminium). The good part is I can swap back to the stock JCW anytime I like because I have not modified it at all, change over only takes 10 mins.