Invalidating car warranty
It's also illegal for a dealer to deny you the OE warranty because you have changed the exhaust system. But you will need to be armed with some basic information.
Under the Magnuson Moss Warranty Act of 1975, 15 USC, 2302 and Clean Air Act 42 of USA code 7541, you have rights. The answer is “possibly,” as the increased stress to these components cause by the increased power output from the turbo could indeed cause your warranty to be denied. Since most high quality systems, at least those systems that are 50 state legal, are installed behind the catalytic converters, there should be no warranty concerns to other components, even emissions components.
For instance, some people believe that adding a simple performance part (like a custom exhaust or after market air intake) will somehow endanger your warranty.
Remember: the engine creates the emissions, the exhaust system is the path from which they exit.
A freer flowing exhaust will not do anything to inhibit emissions expulsion or to increase emissions output, all of which is controlled by engine management and the catalytic converter(s).
However, in my years of experience in the car business, I can tell you this is rarely true.
In fact, federal law prohibits auto manufacturers from denying warranty claims in most cases.