Maybe, but bottom line it's hardly anything to write home about. I have the HKS. Very, meh.
Per below, you're obviously coming with the pipes (H, mid, muffler). I went the overkill route just to be one-and-done at the dealership. Replaced every small part since my car had 30k mi on it anyway, and at that point you don't know if a bolt will strip in the process. I believe it's the 20606 rubber mount that either gets skipped or is substituted with a longer piece because the Nismo has a weld that makes things line up differently. I'm almost certain this was skipped on my car.
If you go this route, just be clear on the fact the gaskets are a bit different. Dealer originally thought the MA and MB gaskets would be identical, but that's not true. A lot of people just swapped straight up and reused their old gaskets. You can do that, although I think the non-Nismo gaskets have a smaller bore — but not like that's the end of the world.
Yes and no. It depends. The Nismo 370z mostly sees the marketed gains because of a tune. If you had no tune prior, you likely won't notice it for better or worse.
I had a tune for my stock exhaust setup, then switched exhausts, and noticed a lagging feeling. It got quiet, too. Got a dedicated tune, and I don't think that low end punch was ever the same. Maybe I was getting too used to that kind of performance at that point. Who knows.
Basically, if you want some gains, you get the tune, but if you're outright looking for gains (and sound), look elsewhere.
The Nismo exhaust only has the merit of keeping that OEM feel, which was what I was after. The underwhelming silence probably saved me a few times now.