This is great Info I am having the same problem woth my fast xfi system and mostly at idle.
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You shouldn't put too much stock in AFR readings at idle, especially with a lumpy cam. You set it so the engine is happy and the AFR is what it is.
With a cam with a lot of overlap you get a lot of random misfires or half fires at idle and all the oxygen that doesn't get used parades past the O2 sensor and you get a lean reading when in fact it could be/likely is pig rich.
