Here....

Interesting video, thanks for sharing. Interesting note about the Y piped exhausts at the end there. It seems like Y pipes and a single exit seem to be beneficial on our cars as well- at least from my reading.

It does appear that an X-pipe does offer better high speed flow and better low speed scavenging effect over an H-pipe. Furthermore, it appears that a more open-type X pipe improves on those qualities. Interesting! I’m just wondering when is too much. In my case, I have noticed a definite improvement in engine smoothness at high revs with my Ark DTS catback.

GReddy Evolution GT for the win!
 

I have the GReddy Evolution GT catback exhaust with Fast Intentions high flow cats and it is loud but once it's warmed up it's not too bad. It's definitely a cleaner and overall better sound than if I had test pipes. Also, that catback keeps the OEM exhaust tone while enhancing it.

It flows pretty good mid-range to redline. I found that I lost a little bit power, mostly torque, below 3500 rpm.

The sound is very nice and my friend who has a Magnaflow on his G37 likes it a lot ;) I read somewhere that the Nismo OEM exhaust was made by GReddy but don't quote me on that.

Actually the OEM Nismo exhaust was made by HKS. Having removed it I can tell you that it nothing special and was made to a certain price point. This means that it has approx. 2 inch diameter piping, MIG welded (not TIG) and the H-pipe section appears even smaller. It has "dirty welds" (not smooth) on the inside of it. I doubt that there is much scavenging effect. Furthermore, the back muffler section does have better flow than the standard muffler but it is extremely quiet. My grandmother's Camry is probably louder. I personally think Nissan completely and royally dropped the ball on the Nismo exhaust and relied more on the fake exhaust sound inside the cabin to make up for no exhaust sound outside the car. But, luckily it is easily fixable with the numerous aftermarket exhausts available for our cars. :driving: