Will "X" modification void my warranty?
Yes and no. Your warranty can not be completely "voided" due to modification. However, if your mod caused something to break, then the broken part will not be covered under warranty. The rest of the car is still under warranty though. For example, I'm running a nitrous kit on my car. My entire engine and drivetrain warranty is out the window. If I broke something like an axle, it would be said the extra power from the nitrous is what caused the axle to snap and it would not be covered. But if one of my windows broke or my speedometer stopped working or something else like that which has nothing to do with the nitrous happened, it could still be covered under warranty.
As the saying goes, "you gotta pay to play".