Most likely Porsche could point to the mods and deny with no EPA problems.
http://www.epa.gov/obd/pubs/420f09048.pdf
What Are Specified Major Emission Control Components?
There are three specified major emission control components, covered for the first 8 years or
80,000 miles of vehicle use (whichever first occurs) on 1995 and newer vehicles:
• Catalytic converters
• The electronic emissions control unit or computer (ECU)
• The onboard emissions diagnostic device or computer (OBD)
Catalytic converters are critical emission control components that have been installed on most
cars and trucks manufactured since 1975. Since engines don’t burn fuel completely during the
combustion process, the exhaust contains a significant amount of harmful pollutants such
as carbon monoxide, hydrocarbons, and oxides of nitrogen. The catalytic converter aids the
conversion of these pollutants to less harmful substances such as carbon dioxide, water vapor,
nitrogen, and oxygen before the exhaust is expelled into the environment.