Just traded in my 2000 SE 4x4 for a 2005 SE 4x4. Nissan's seemed to have addressed most of the issues with the earlier models: slow, rough ride, poor mpg. So far so good, but now I'm greedy. Already put a K&N filter on it. Okay....now about the exhaust.. Anyone besides Gibson have one yet? Not that I have anything against Gibson but a choice would be nice. I've talked to several people about the cat-back exhausts and heared that they don't do much but make the truck sound "cool". Big deal, how about performance? Anyone Dyno the Gibson on the 2005 yet? How about the intake systems....Nismo, K&N, etc... anyone Dyno any of these. Bottom line: For $700 bucks (exhaust and intake) will I get a "significant" increase in HP, torque, mpg...?

What is your definition of significant. The best you can hope for is 10-15 bhp gain.

If you want significant gain go with Nitrous.

That's not too bad, $50-60 per HP. I'd imagine that most the gain is at 4000 rpm and higher....Checked Jetchip, around $350 for 8-10 hp all at 4000rpm or higher.