Hmmm... Usually, you'll get a solid CEL AND the blinking cruise. Anyway, if it is the cat inefficiency code, then I think you get some o2 sensor simulator to send modifed signals to your car's computer (or something like that), or if you have a hi flow cat, I think you can buy some sort of spacer for where your o2 sensor mounts to take the o2 probe a little further out of the exhaust stream.

Do a search on this stuff, as more qualified people on this site will be able to provide more detail.

Jason