As far as I know, the whole "voided warranty" conception is either outdated or just wrong. If you bring in your car for a repair and they attribute the cause to a modification you have done, then they will not cover it. They don't completely just void out your warranty.
If you put an ECU tune on your car and you bring in your car for a suspension repair, they aren't just going to not cover it. Now I'm sure there are going to be dealerships that play loose with how they judge if a modification was the cause.
As mentioned by UJX they won't deny suspension warranty for a tune but they most certainly can/will void your entire powertrain warranty even if you just have rev hang disabled.
This is very common in the VW/Audi world. Cars will get tagged as TD1, which is their internal designation for a car with a tune. Once your car is tagged as TD1 it will be flagged at any dealership when your VIN is entered.