I have worked at dealerships for over 30 years and here is how something like this is looked at. If you modify the air intake system the only way they care is if you come in with a problem involving the intake such as dirt ingestion or restriction of air flow, keep in mind any sensor having to do with that is included. This involves only that repair on that day and if you returned the car to its original condition and returned they would then repair it. I know of nothing other than a car that has been submerged in water that can totally void a warranty. If you have a dealer tell you your warranty is voided ask for that in writing so you can have their you know what. Warranty will pay to repair the vehicle in its original state and anything you change is warranted by the installer (or yourself) including progressive damage. The enforcement of this is up to the dealership, some will not care and some will be hard nosed about it.