Ok, just got back from a local shop. The guy said HR y-pipe will work with Nismo exhaust. He also got a 350z, so he knows what he's talking about. He said the hr y-pipe produces less drone/rasp than the Nismo y-pipe.

I will swap out the stock exhaust with an used Nismo exhaust with hr y-pipe plus berk hfcs this week. Then I'll try to switch to Nismo y-pipe and see if any sound difference.

 

We could of told you that info, nothing new.

I don't think HR Y-pipe reduces drone/rasp compared to the NISMO version. My HR y-pipe still has raps and hisses like a madd cat (got test pipes with stock catback)