Of course it makes sense. Nissan warranties their Design, specs and tuning parameters. When you start changing that, Nissan has no control over the effects those changes may have. Most all manufacturers have the same guidelines. If they didn't engineer it, they're not gonna stand behind it. You're on your own there..Nissan has no obligation to pay for your modifications (or screw-ups)..

THe truth of warranty is this:

ANY part added to the car can void the warranty as long as that part is the direct cause of the issue. If you put an exhaust on the car and your AC fails or your windows stop working, they are not related, no warranty issues there. However if you put an exhaust on the car and consequently the cat cracks because you overtorqued a bolt, well, no warranty.

Standard bolt ons usually are not a problem with many dealerships, however it is up each dealer's discretion on if they wish to work on the car in the first place or not. You simply cannot avoid that.

so you'll be fine as long as you install things correctly and don't do anything too too crazy. BUT if you do, it should not void the ENTIRE car's warranty.

hope that helps (and this is coming from someone who's working in dealerships for over 8 years)...