Magnaflow Performance Catalytic Converter for Mazda RX-8 2003-2012A bad cat can restrict flow, lower fuel mileage, impair performance and even cause engine problems. A Mazda replacement can cost well over $1200. 00. This High Flow cat can solve your problems while helping improve your airflow and releasing a little more of the distinctive rotary sound that your 13b makes. Not only that but it will save you money while doing it! A direct replacement part with the O2 sensor bung after the cat. Fits 04 11 Mazda RX8