Hello, A week after my son replace my Opti--A po420 code came up, i replaced the post o2 sensor on bank one--week later code came up again--my thinking is now to let Midas cut and splice my OEM cat on the driver side, i have now a Mac "Y" pipe with dual cats--dumb ideas?-Car burns rich and at stops has an exhaust smell inside the car with the air on. Would splicing that cat help or just be to much trouble Thanks Dwayne

 

So will that help my problem?????? Or at least some of it?????

 

Swap the after-cat O2 sensors side-to-side. If the problem follows the sensor (P0430) it inidcates the sensor is faulty. If the problem stays on Bank 1 (P0420) it indicates either the cat is deceased, or you have a wiring problem.