Man, all this talk about "voiding warranty" on every car forum I'm ever a member of drives me crazy.
Look up the Magnuson–Moss Warranty Act people!!!
The manufacturer HAS TO PROVE your aftermarket/modified parts caused a part to fail, it's on THEM to prove it. Swapping out a turbo would ONLY void the warranty on the factory turbo, along with any other FACTORY part that was replaced during the swap, unless the dealer/manufacturer can PROVE that the modded part caused other parts to fail.
SEMA has a whole team of lawyers that will help people fight these cases, and they almost ALWAYS win.