Originally Posted by Cfichman
Even if you leave it in and they find it they can't just void warrenty, they have to be able to prove what you installed caused damage.
Actually yes they can. In the U.S., dealers can and do deny warranties as they choose due to people modding cars when something breaks in the car that can possibly be tied to the mods. But you the consumer will have to spend thousands out of your own pocket to sue them under the Magnuson–Moss Warranty Act to fight it to get them to cover it. Is that something you really want to deal with? Oh, and while you're fighting them in court for months, they're not going to fix your car on their dime until ordered to do so....so guess who is going to have to come out of pocket for the repair and legal fees up front? That's you.