It's the years. I'm not sure if it's the 04 or 05 when they started it but they all have cats on now. On the window sticker it says "California Emissions System NO CHARGE". Like we wanted that crap to begin with! I don't live in CA so I'm not too worried about it till inspection time comes around. I still have the cat so it won't be a big deal to fit it to a pipe and stick it in for a day.