there is a rattling noise coming from under the truck when accelerating.

Crawl under truck and with 'rubber' hammer tap on entire ehaust system to locate rattle... possible cat converter breaking apart also....

Agree with pushrod.....probable cause loose cat. converter heat shield, or exhaust component.

Look at the tailpipe - at very back of the truck. See if its loose....mine makes same noise and tailpipe is coming away from the flange connector near rear axle. I'm hoping Nissan warranty covers this.

I found that in my '04 it was the heat shield surrounding the exhaust pipe vibrating during acceleration. I just installed pipe clamps around them to snug it all up. I hope your problem is that simple.