The 97-99 USA cars have only the rear cats, and what is shown in the link above is generic weld in rear cats. On the 2000-2004, the USA cars have 2 sets of cats, and that first set that is integrated into the "headers" is the set that is monitored:
I have a 2000 S with around 137,000 miles, and ever since around 103,000 miles (when i got the car) I occasionally got the cat efficiency codes. With replacing some O2 sensors that were aging, etc... I was able to clear up these codes, although looking at the real time data using the Durametric diagnostic tool, I could see that the cats were nearing the end of their life. I replaced them with a pair of take off cats from a guy that installed race headers on his Boxster, and they only had about 20,000 miles on them, and so far they are working great.
If you got some used ones from a car that had lower miles, you could probably get years and years out of them. I replaced them myself, and while it was a hassle, it is doable by a "regular" person. I hit all the bolts with Kroil and let them soak, and didn't have any snap off.
I have replaced my 2nd cats with "test" pipes, and if you are changing your front cars, this is the perfect time to change those pipes. That 2nd set of cats isn't monitored so it doesn't throw any codes, and it does add a nice little enhancement to the sound, while not making your neighbors mad
I used new hardware that I got from Fastenal, I don't recall the threads, etc, but take some of the old hardware up there and they can match it up for you.
Threaded Mode
