Well, from some experience, mostly in domestics, this is what I can say.
The Cats have little in nothing to do with the O2 readings at the tail pipe. If you wanted you could, but some sort of bung in the exhaust, the wideband would not have to be welded just supported for the pull. Then you could test it for sure. But from experience I can tell you it does not matter.
Second I do agree that the computer richens the mixture when the mods are done, and it re-learns what is going on and returns to the factory Fuel and Air ratios. The Ford computers do the same thing. However has anyone tried to use an AFC or some sort of fuel management to cure this. With the AFC you could tune the truck with the MAF, lean it out, and gain the performance. I was going to do this for better gas milelage. 12:1 is too rich for the street NA motors. I think this is some of the problem with the S/C guys running 12 psi of boost and not making but 80 more hp. Theoretically if you double the pressure in the motor, you double the power and 12 psi is almost 2 atmospheres. Of course it is minus parasitic losses, but non the less it should be more than a 80hp gain.
Of course I just bought my Tundra and have no data, but this is mostly Theory and Fact. If anybody has insight please let me know.
Jason
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