Awesome, thanks for the Intel, will do that next. The CEL inspired me to buy an OBD reader to reset the codes, which is handy because the traction control gets dropped with the CEL.

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I have 05 t4r v6 with the same codes at first i had a P0430 code and i replaced both of my o2 sensors no cel came on for a while but after putting on 2k miles the light came on but this time it was p0430 and p0420 both of these codes are for the catalytic converter I'm going to end up replacing both cats and i think you should too

Just as an FYI, and hopefully this helps someone else.

I have a '08 V8 4WD 4Runner that was giving me the P0430 code. I've read both that it is on the driver's side and passenger side, but most seemed confident that it was a driver's side issue on the V8. Wrong.

I tried everything on the driver's side: new O2 sensors, new PCV valve, anti-fouler plug, etc., but nothing worked. The code kept coming back, more frequently, and eventually within a day or two each time of clearing the codes.

I finally tried the shop-vac blowing into the tailpipe trick to find exhaust leaks and found a large one between the cat and downstream O2 sensor on the passenger side. Got that exhaust leak fixed and the code hasn't been back.

TLDR: On a V8, the P0430 is a PASSENGER side cat/sensor issue.

JUST THROWING THIS OUT THERE, IT MIGHT HELP SOMEONE.

so had these p0430 and p0420 codes for about a year now. decided to try an experiment. installed a spacer on bank 1 sensor...and used toilet cleaning liquid to soak and wash bank 2 sensor. have driven over 200miles and the MIL codes are gone!.....meanwhile my mechanic had already prepped me for a CAT replaced, before i decided to give the mod a shot