Got a notice from DMV for a smog check.

My SES light is on. Code P0420. It's been ON for a while (> 10 months)
I am gonna clear it and take it to smog check.

If that doesn't work, which cats need replacing.
Front, Center or Rear?

I get confused but it's either the front or the center if replacing the O2 sensor itself doesn't clear the code.I fixed my front O2 sensor code by hollowing out the cat and spacing the O2 sensor out with sparkplug antifoulers.Code has been gone for years.

P0420 is for the bank 1 (firewall side) pre-cat that is built into the y-pipe.

How much $$ is a used or after market y pipe?

I couldn't find any videos for DIY. How much time would it take for a mechanic. 1-2hrs?

I think OBX can be had for $200ish. You'll likely have fitment issues. Have a shop mod it for the extra $60-80. Cattman is your best bet, but good luck finding one. I've still got mine. Over 100k miles on it and never a problem.

Where can I find OBX.
Google wasn't helpful.
Can't find anything on cattman, only discussion forum results.

Add 3 ounces of TCW-3 per tank full to about 5 tank fulls of premium gas and it might clean your cats enough to pass. TCW-3 is an outboard marine oil that cleans cats and o2 sensors and lowers emissions. We call it Blue Velvet. You can get it cheap at Wallymart for about $3 a bottle.