My biggest concern before install was smell, especially since I almost always drive topless.
Expecting the smell of rotten eggs, I was pleasantly surprised by the aroma of gasoline. It's not that strong either.
Definitely louder than stock, but not as loud as I had anticipated from watching videos. I do kinda like the tinny whistling spooling sound though. The downside is that I hear less of that sweet vacuum whoosh from the DCI.
As far as performance, there is a noticeable difference, especially low end. Traction control definitely kicks in more often too. Though the real benefit is being able to up the tune and run more boost. Amazing overall gains for the price, highly recommend.