I was reading a article on the development of the C5, LS1, and LS6. Apparently the C5 Chief Engineer stated that in 1997 they changed the calibration to basically stay in closed loop even during power enrichment and WOT. Apparently he said they did this by going "slightly rich of stoic"?
I've looked through all the early LS1 PCM files I can find and I don't see any evidence of this statement being true, but I find the source creditable:
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I personally am I big fan of tuning using the stock O2 sensors at WOT by forcing the tune to run stoich all the time. I know people have it drilled into their heads that if you run stoich at WOT for even just a second your motor is going to blow up. I haven't done the math to calculate the extra heat capacity provided by the extra ~15% fuel at WOT/PE. However just guestimating I bet its only about probably 1 hp, but nevertheless would be a very interesting calculation to do and shouldn't be that involved.