Those calibrations are pretty much only done for only emissions, it's interesting to play with the O2 gains and watch an analyzer. I used to play with a mechanic's 5-gas (NOx/HC/CO/CO2/O2) and if you have one of those you can find some interesting things happening when you tune it. I now get to play with a Horiba 5-gas rack (same five results but the analyzers are better and a 5 second response time and 1 second T90 time). A cat sometimes wants some O2 storage/release to stabilize conversion efficiency although with a postcat O2 some cats work well with as low a storage/release as you can get away with - I have run systems with a wideband in the front and no toggling and great emissions. Put on a different cat with a different formulation and it needs to be hit with lambda steps of +/- 0.05 (10% total swing) to get decent emissions. You can drive yourself crazy looking at the numbers sometimes.
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