Smog (Cat) question for the experienced 2006 Tacoma

Okay, here's where I am on this.

I just replaced my head gaskets, intake gaskets, PCV valve and hose, valve cover gaskets, passenger side valve cover breather hose, cleaned MAF, spark plugs, Air filter, Oil, Upper and lower exhaust gaskets, Up and down stream sensors (Denso). Used Cataclean more than once.

Still get the 0420 after about 50 miles. Last thing are the Cat's. My question is, being that it's just kicking the bank 1 side, is it possible to just replace that Cat. Or will it be so clean, it could trigger the bank 2 side that's older. I don't have enough to buy both sides, just had to sell a generator to get the money for one. I 'm buying OEM, I'm in California, so I don't want to mess with aftermarket. Been messing with this for a couple months to pass smog, at the end of my 8 week temp permit, and they wont extend it. I showed receipts proving I've been addressing the issue, but they don't care.

Anyone have first hand experience with this situation.

Thanks,

 

They dont relate to each other, but the other cat is very likely on its way out. You can change one at a time, it doesnt affect one another.

 

Thanks for the quick reply, it puts me at ease for a minute. I'm having nightmares of that CEL, It's haunting me.