for a quality thread - lots of good info here.
FWIW, I started experimenting with E85 about a month ago based on a post from VNeBLOB42, and it's definitely cleaned up my timing issues from California's ACN 91 octane "piss gas." Full disclosure, I have gotten a few fuel pump codes while using the off-the-shelf COBB maps (St2+ Aggressive and St2+ Sport), even though I never blended more than 3.2 gallons of E85 to a full tank. No issues while using E85 on St2+ Drive (yet).
Take-away, I don't want to scare anyone as I'm just figuring out the right ratio to run for my car. I'm really pleased with the results so far and plan on continuing using E85 as the car's running better than when I was blending in race gas as an octane booster.
Eventually, I'll get a Pro-Tune to use E40 or E50 and will probably end up doing some type of Low Pressure Fuel Pump (LPFP) upgrade. I'd rather not mess with the OEM LPFP, but don't know how to swing the additional LPFP used in series with the OEM pump without using the JB4 like some of the guys are using on the "other forum."
Oh, and I store (qty 3) 5 gallon tanks of E85 in my garage to blend in with ACN 91 since the nearest E85 station is 20 minutes from my house. No issues with water absorption so far.