Quote Originally Posted by DrkPhx View Post
FWIW - I wouldn't change stoich on a LS1 PCM based on supposed E10 ethanol content because the mixture can vary from gas station to gas station and even brand to brand. Here in MN, all gas is ethanol based (with a few rare exceptions), so it's a fact of life. Some of the newer stations have pretty good in-ground ethanol sensing equipment that allows them to monitor the content of each tank, but some don't. Most of the dealers also have ethanol content testing equipment to check fuel content when vehicles come in for warranty work for related repair. You would be surprised how much variance there is even from one station.

I've done a few test tunes with different stoich and fuel combos and always come back to the factory stoich and E10 93 octane for my TA for the best overall results. My .02
The constant being that there is always SOME ethanol, with an "ideal" ratio of E10, it would make more sense to set the tune to the correct E10 stoich ratio and let trimming take care of the 2-3% swings either way. The alternative has fuel trims consistently 4-7% higher than they would be based on airflow calculation inaccuracies alone.