[8ball]

What year is your Titan? I would just go single side and get a 22" Magnaflow flow through muffler. With the headers you have now you still need to get UpRev to run properly, but tuning is not an issue because UpRev will do everything, you just need to do your logs, which is pretty simple. After your logs you email it to UpRev, they send it back, and you upload it to your ECU. If you go true duals I personally would go no bigger than 2.25" pipes solely to maintain torque. There should be some good info here and on Club Titan regarding your setup. I have had a real dual setup before, the Nismo true duals. With headers it ran a bit sluggish until I had everything tuned by UpRev, I needed more fuel. LOL

Out of curiosity, where did you get your Nismo headers.....?