Isn't that over the stock exhaust and not the Nismo with the H pipe though?

You are correct.

Correct me if I am wrong here, but from looking at pictures it looks like the Stillen has a Y pipe rather than the H pipe of the Nismo exhaust, how can this exhaust offer more performance if flow is restricted so early on in the exhaust?

Edit: Added image below to show what I mean
https://images-na.ssl-images-amazon....L._SL1200_.jpg

I meant 18 more hp over non nismo stock exhaust.



H-pipe and X-pipe are the better options over the y-pipe.

http://www.the370z.com/intake-exhaus...ifference.html


https://www.drifted.com/370z-exhaust-guide/

Just buy a stock mid pipe from a non-Nismo and you can mate that with the Y pipe you got now and the short tails. Should cost about $1-20.

Will the diameter of the pipe be the same though? Additionally do you have a part # or know where I can find one for the stock midpipe?

Thanks!