technically( this according to the Nissan dealership I go to) making any type of modifications to a car not done by an authorized technician will void the warranty, for instance if you have a voltage spike and it fries your cars computer, well then they will attribute it to the amp you are running, or the fact that you installed aftermarket stereo equipment, its all some shit to tell you the truth, I was worried about it last year but said **** it and went with it, later
It all depends on your dealer too. I talked to mine before I went and did a lot of stuff and they were pretty cool about it. Same thing with the engine, I asked about what I could do and the guy said just bolt-ons. Any internal engine work would void the warranty. Obviously, if something goes wrong with the aftermarket part they aren't going to cover it, but anything else they will still cover. I think you just need to find the right dealer and be real nice to the service manager. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
I forget exactly the details but if any alteration or change in equipment is BETTER than OEM, it cannot void your warrenty if installed properly. So throw that aftermarket alt on and dont worry about it.