I got a P0139 code-O2 sensor bank-cat slow response. Does this mean my cat is going? Also I have 87,000 miles on my car. What is the emmisions warranty on a 04 RX8? When does it expire? I searched and couldn't find

* Specified major emission control components are covered for the
first 8 years or 80,000 miles of vehicle use.

http://www.epa.gov/obd/warranties.htm#1

Emission Warranty is 8 years / 80,000 Miles. Looks like someone is getting a Hi-Flow Cat Soon.
http://www.epa.gov/obd/warranties.htm

How much for oem cat from Mazda? How much for hi-flow cat and where could I get one?