I am still amazed after many years how well all the parts of an engine work together and at the speeds that they do. Cruising down the highway at only 2000 rpm in OD, each of the 6 cylinders is firing around 17 times/sec. Each of 12 valves are opening/closing and each spark plug is firing at the same rate - all in near-perfect synchronization (not to mention injection of a precise amount of fuel just before each cylinder fires. To hold the parts in your hand and put them back together into a working engine gives you a much different perspective. It also can be a big source of pride that few understand, and strangely can make you like your vehicle a lot more. You did a first rate job fixing this one.

I personally can't recommend the non-foulers to attempt to circumvent having a catalytic converter. Don't really see how they could truly work, anyways - doubt if they really slow down the O2 sensor response time so much that the PCM thinks there is a converter present retaining oxygen (during the tests that it constantly does). But admittedly I've never tried it. I always thought of using the non-foulers as being a form of Urban (Internet) Legend that has been spread without merit. Once a poster thinks they fixed something, they are unlikely to post another time admitting they were wrong - so it gets propagated as being valid. I never thought it made any sense, so I ignored it. (Just like many popular fixes start by replacing O2, or crank, or MAF sensors - because replacing them "fer sure" fixed someones vehicle)

 

You couldn't have said that better Les, it's a totally different feeling driving something around that you put together yourself. Thanks for this information about the non-foulers, I looked into it a bit more and it seems for some people the SES light does come back after a while. I'm not sure what I'll do now but I'll figure out something to keep that P0420 away, a new cat is just so expensive especially since we don't have any emissions checks here ever. Thanks Christine, lol I need that better mileage right about now. My other car that I was driving has a 2.5L inline 6, compared to the 4.3L V6 it was practically free for gas!