Does this 2003 Tundra need new catalytic converters?

I'm thinking that this 2003 Tundra that I'm working on needs new catalytic converters. There is a check engine light on. My friend took it to a mechanic. The mechanic said that it needed new catalytic converters.

But before he throws $800 at the problem I wanted to test it myself to verify that the cats are actually bad. So I made this video of my test.

Every detail that I could think of that would matter is in the video!

What do you guys think?
Does this Tundra need new cats?
If not... where did I go wrong?

https://www.youtube.com/watch?v=4H3m2g1Ine0

So I found out that the down stream 02 sensor ( called rear O2 sensor in this vid ) is expected to fluctuate a certain amount simply to prove that it is installed and working.

Does anyone know how much the expected amount of fluctuation is?
Maybe this truck just needs new down stream 02 sensors?

Ok, so I found some more info including some live data of a properly working upstream vs downstream O2 sensor.

At first I thought that the purpose of having the downstream follow the upstream was just to simply prove that it was there and installed... but apparently this has to happen because it's not practical to eliminate all of the oxygen from the exhaust.

Based on this chart, it looks like the downstream is finding that the oxygen level has been averaged out. I'm not sure how this makes sense, or how it helps the environment... but since the voltage fluctuations are so low on both of my down stream O2 sensors... I think it's safe to say that they are bad.


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