Hi All. I wanted to share that even though K&N doesn't officially make an air intake replacement kit for the Nissan NV, I crossed my fingers and ordered the kit for the Nissan Xterra, and it worked!
I have a 2013 Nissan NV 2500 HD V6 with high roof. The motor seems to be Basically the same as the Xterra and the Frontier. I just looked at photos of the motors and betted that that it would work. What does need some custom fitting is the box housing for the cold air intake: Because the mounting points of the stock intake on the Xterra/Frontier are different from the NV's, you'll have to bend a couple of the mounting brackets that K&N gives you, and drill & tap a couple holes into the frame of your NV to be able to mount the cold air intake box thing. Other than that, fitting the main intake tube was not a problem. I didn't have to bend the rubber connections much (or at all) in order to get it to face the right direction, and the hose and electrical connection worked out just fine. I did have to get rid of the stock engine cover which is connected to the stock intake tube, but... oh well.
The result is that, as many describe after installing aftermarket air intake kits, the throdle is a little more "responsive". Basically it reacts a little bit (but noticeably) quicker off of the line. I did not notice a difference in sound upon simply starting the car, however upon throdling, especially when putting the pedal to the metal, the increase in acceleration is not huge, but definitely there. You can feel that the air flow has opened up, and the sound is nicer... not at all loud, but ever so slightly more aggresive, and with a slightly lower pitch. I've literally only driven it from the place it was parked to the muffler store, but in that short ride I could easily tell the small difference. I didn't get any engine lights or anything, so that's good. Now the NV is at the muffler shop getting a Magnaflow 18" muffler replacement. The stock muffler is a 22". If you don't want the NV to be loud (which, I don't), Magnaflow recomended that I do not get anything less than the 18" replacement. The guy at the muffler shop told me that if you get the 24" replacement it might be even more quiet than the stock. I don't want to grab attention or be annoyed by exhaust noise in my car, yet I would be a little exited by a little "vroom", so I just decided to go with the 18". I'll write about what I notice after getting that installed too.
As for the air intake just go to K&N's website and punch in for the Nissan Xterra. I forget exactly, but I believe the kit works for years 2012-2015. As for other years, I don't know if that will work and you might want to take a real close look at photos of your engine vs. photos of Xterra/Frontier to see if the angles are right for the intake kits. I also don't know how this would work for the V8 models... however, the V8s in the Nissan Titan are said (word of mouth... don't quote me) to be the same as the NV's V8.
If any of you have success or failures installing aftermarket air intake kits on your year/engine size, do the rest of the NV owners a favor and post here... for, as you all probably know, finding aftermarket parts for the NV is HARD... and annoying. Had I known that almost nothing is made for the NV in terms of aftermarket parts, I might have chosen a different van, but, I'm glad to know I can gain roughly 12 horsepower by replacing with a K&N aftermarket air intake kit. I got the cheaper plastic option (not the metal tube) because it apparently gives slightly more increase in horses, and ironically is a little cheaper than the metal tube replacement.
PS, I live in California so I got the CA legal version.