Somehow missed this topic. Here's the law.
The Magnuson Moss Warranty Act requires manufacturers to honor their warranties and auto manufacturers only warrant their vehicles against manufacturing defects. Dodge can void your warranty coverage if you blow the motor with NOS (or whatever, pick your poison) because the failure was not due to a defect in a factory component. It was caused by something added to the car: the nitrous oxide injection system which was not part of your car to begin with. That added / changed part caused a non-defective part to fail. Your mod did not void the warranty. The warranty does not apply if the failure is not caused by a factory defect.
Now, as pointed out, you can go to court saying that the added part had nothing to do with the failure, but that'll cost money and time. And manufacturers love to say "the warranty is automatically voided" even though that's not true. Know your rights and if you have time and / or money to fight it, fight it. I've seen things I could NOT BELIEVE were eventually warrantied because they went through the process. And if you're in my area and have this problem, I'd be glad to help.