I would like to finally get my 4runner inspected again (my tag expired in 2011, it's been my silent protest against taxachusettes), since I have to park on the street alot. I have had a P0420 since I bought the vehicle, and I'd like to finally get rid of it. I am pretty sure I have a lingering exhaust leak somewhere, though I have tried to weld the flanges together to seal it up. The rust is severe along the whole length of the CAT's.

Anyway, I am thinking about either replacing both CAT's or getting a URD O2 simulator.

Here are my thoughts, I'd like to hear your thoughts too:

Replace CAT's: ~$350 from rock Auto for front and back(Eastern Catalytic)
May not eliminate the P0420 because of sensitivity of Toyota ECU
Would hit reset on the rust
Should eliminate the exhaust leak

O2 Simulator: ~$120
Doesn't fix the leak or rust
Cheaper
Not complaint with CARB laws

Let me know what you'd do and why, and any pros/cons I have missed.

Have you checked out Magnaflow CATs? The previous owner of mine had the CAT stolen, and had a Magnaflow installed. Its been close to two years with no codes. We don't have emissions here, so I don't have to get it tested, but I would assume it would. I think they're cheaper than the ones you mentioned from Rock Auto.

Magnaflow 99006HM 49-State Semi-Universal Catalytic Converter | Auto Parts Warehouse

Hmm, that one doesn't appear to have any attached pipes. The Eastern cat's from rock auto appear to have the flanges, pipes, and o2 sensor bungs already welded on, so bolt on. I don't think I could weld new cats into my rusted pipes, and the flanges are leaking anyway.

I don't know how strict they are, but if it's super rusty, they may bawk at that alone. I went through the same struggle and I decided to go the CC route. Although I found a cheap, certified, used CC(s), I still would feel more comfortable with replacing than band-aiding. WHen I got mine out, I could see that the core of the CC had totally eaten itself and was not giving my engine good exhaust flow (I have some pics on here somewhere, maybe my build thread?)... I haven't seen any noticeable fuel mileage increases, but that's not to say you wouldn't either.

I vote CC.

I don't know about MA but here in UT O2 simulators are illegal. Instant fail.

They have the full setup that you're looking for, just didn't link it. Can't recall exact price off the top of my head, but thinking >$400. And as long as they've kept up the quality for a couple years, you won't get any codes.

If your cats are bad you need to look upstream to find out what caused it. Cats don't go bad, they get murdered.

2-3 yeays ago we installed a magnaflow low-flow cat purchased through Amazon. It has never thrown a code, hold on.....knocking on wood, Ok I'm back....and has passed emission each time.

If rust is an issue eventually you're gonna have to deal with a leak. I guess it's aftermarket cat or URD 02 sim and straight pipe repair and all that involves.

I'm a chicken shit and would more than likely go with compliant carb laws option. But I'm live in emission country.

Good luck.......8sm

He's from Massachusetts. Cat killers live on those roads in the winter.

Thanks for the responses guys, I think I am going to replace the cats with aftermarket.

The magnaflow's on amazon are definitely more expensive that the Eastern catalytic's

Anyone have the eastern cats and still have problems with the code?

Just wondering what route you went. Did you go with the Eastern cats? Any code issues? I keep popping the P0420 and am thinking about going with the Eastern cats. More affordable and will hopefully keep my truck from throwing codes. Thinking I will try the URD simulator first though. Thanks.

Why not use a anti spark plug fouler on the second o2 sensor? that will get you passed inspection at least and it shouldnt be more than $5..