Nope, I haven't taken it it for emissions check YET, but it's due shortly.

I think two of the main reasons that cleaning the throttle body may have fixed the cat (the code hasn't come back and I drove it 3 times today) is because I did it:

1)With the engine running

2)With B12 Chemtool Carb and Choke cleaner

The reason I think doing it with the engine running helped the cat is that some of the cleaner got into the cat and either cleaned it up by solvent action or by heating the cat up, or both. The cleaner also cleaned the intake valves and combustion chambers on it's way through the engine.

Much more than just the throttle body gets cleaned when you do it with the engine running.

The reason I think that using B12 Chemtool Carb and Choke cleaner helped the cat is that it has some pretty heavy-duty solvents (especially compared to throttle-body cleaners):

Toulene, Methanol, Acetone, Mixed Xylenes, Methy Ethyl Ketone, Butoxyethanol and Isopropanol

This stuff is so powerful it will dissolve paint!

Some people on this forum have suggested that the use of such heavy-duty solvents like those found in carb cleaner may damage the teflon coating in the throttle body, but I look at it this way:

1)The teflon coating doesn't do much.

2)There's no evidence that carb cleaner damages it.

3)If I'm on the line to spend several hundred dollars on a new cat, I don't care about the teflon coating.

Based on my experience here, this what I would do if I were in your situation:

1)Use about 1/2 of a 16 ounce can of B12 Chemtool Carb and Choke Cleaner to clean the throttle body with the engine running. Rev the engine as you clean it. Spray it in until the engine starts to slow down, then stop spraying until the engine speeds up. Repeat this process. There's no need to use a brush to clean the throttle body when using B12 Chemtool.

2)Replace both upstream oxygen sensors, to provide better fuel mixture control so the cat can operate more efficiently. Oxygen sensors do degrade over time and if they have over about 60,000 miles on them, replacing them will help. They start to degrade long before the check engine light ever comes on.

Don't worry about the downstream oxygen sensors, they RARELY (if ever) cause a P0420/P0430 code so save the money for the upstream sensors, the ones that really matter.

3)Replace the plugs/wires if they haven't been replaced in a while.

4)Put Chevron Techron Concentrate fuel injector cleaner into the gas.