The X pipe muffler sounds like a gimmick. It is one thing made to 2 do things job and it probably does each job okay, but not as good as the original part. Dual in and out, single in and dual out etc are usually for packaging and cost. I would put a real x pipe on it or a real H pipe and true dual exhaust.

The Titan does have a funny firing order but I don't know if it has much effect on how the exhaust does it's thing. But I do know there isn't much out there for Titans in the way of headers and if you're leaving the stock manifolds and cats then you're probably way over thinking the cat back. I would just put a decent single 3" or dual 2.25-2.5" on it and let it run.

I assume if the exhaust required some very special setup that nissan would have addressed that instead of putting your everyday log manifold on the truck.

As for the specific question, I have never heard of the Titan needing special exhaust, and most of us wont have because this is a GM truck forum, so most of us only know GM stuff. I am a tech and work on all makes and models, so far I haven't seen anything that makes the Titan a unicorn. The exh setup is like any other out there from the factory.

Old thread, I know.
 

I have the Magnaflow X-pipe muffler on my 03 Silverado SS. It previously had a 2/2 Flowmaster on it. The Magnaflow greatly improved the sound and actually improved the seat of the pants performance without any other mods. This is from personal experience, not what I think or what I've heard.

I know this is a late response to an old thread; posting observations in case someone else finds this thread on a search as well.

Not trying to be a dick, but 99% of the time seat of the pants gains are what you think...people report placebo gains all the time. when I was 16 the tornado throttle body spacers gave me SOTP gains. I floored that vortec v6 everywhere to show off my gains :)