Please get an H pipe. Thats what I went with because I wanted to retain the true dual setup of the Nismo. AAM makes a Hpipe/Midpipe that bolts right up to the Axelback. Ill let you in on a little secret. Hpipe evens out the flow causing there to be no hiss upon releasing the gas.
Here's a video. Second video skip to 6:49
370Z Nismo Meisterchaft Axelback AAM 2.5" Hpipe Resonated Midpipe Revs - YouTube
370Z Nismo Sunday Cruise - YouTube