02 non fouler spacer, what works?

I have an 04 2.4l. The engine was overheating and turned my cats to dust. I had the top end rebuilt and now its running great. I can't justify spending hundreds on cats that might not work on a truck over 20 years old.

I spaced the downstream 02 and gutted the cats. It got rid of my P0420, but now I am getting P0136 02 sensor code. Ive taken the spacer out and shortened it twice and am still getting the code.

Do I need to replace the downstream 02? Or is my spacer still just not at the right depth?

 

if you did the above only cause for P0136 would be exhaust leak or melted/unplugged O2 sensor pigtails

 

https://www.engine-codes.com/p0136_toyota.html