nice diagram, im curious how the Stillen setup looks, can you do one of them?

The diagram posted is of the stock Z exhaust (in yellow) and the NISMO exhaust that comes factory installed from the dealership (in red).

According to Nissan, it is responsible for 50% of the 18 horsepower difference between the basic Z and the NISMO. This is a completely different exhaust then the NISMO S-Tune, that is available as an after-market add-on from the dealership, or from your local performance shop. The NISMO exhaust in the diagram (factory installed) is actually better designed then the S-Tune, because it is a true dual exhaust. Although this diagram shows a y-pipe configuration towards the front, this is just from an outward appearance. There is heat shielding on the outside, which gives the outward appearance of a single pipe, but in fact there are two separate pipes underneath.

The issue with the S-tune is that it still has a true y-pipe configuration that comes together in to one pipe, and then eventually branches out in to two again, just like the stock Z exhaust. Although the muffler on both exhausts (NISMO & S-Tune) appears to be a single unit on the outside, it has two internal chambers that are completely separate.

From what I understand, the factory installed NISMO exhaust is good for a nine horsepower gain. Because of the different configuration, the after-market S-Tune will add less of a gain.

If I were going to go with a NISMO exhaust, I would suggest you find someone on here selling their slightly used NISMO exhaust off of their NISMO Z, rather then buy the S-Tune. you will spend a lot less and gain more HP.

Just my $0.02 worth.

Get the Stillen, I love mine. It has never had drone, didnt when i had that alone, doesnt now with full bolt-ons. The Stillen has a different sound than the rest of the aftermarket exhausts out there...

If comparing STILLEN vs Nismo, STILLEN all the way. Nismo IMO is overpriced for the performance.

If your strictly looking for HP and not worried about the note or the price, get something other then the NISMO. If I hadn't gotten a slightly used OEM NISMO, I would have gone for the Borla. I've had Borla products in the past. All of which have been quality products.

I got a used OEM NISMO because I like the way it looks and sounds, and the price was right. It was a good fit for me, but may not be for everyone.