Do you guys down under have any laws protecting warranties? Here we have an act that states a warranty claim cannot be denied by the existence of a modification; they would have to prove the modification caused the failure.
This is just anecdotal, but, I have had two cars now that were tuned, and I've never had any issues with the tune itself, or the service department when taking the car in. Also, no one on any forum I visit has mentioned any issues either, even one guy on the Mustang board whose tuned engine blew up.