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All I know is what happened to my car. Bought in 2006 new. Stayed mostly stock until May/June 2017 where it was upgraded and tuned for E85. February 2018 is when my intake valve seat started leaking. My best guess is E85 pooled on back side of intake valve where it eventually leaked. I also had pitting on multiple valve seat/lower runners. Maybe my local E85 station sells dirty fuel or my fuel upgrades/install were not very cleanly installed where crap entered fuel system and dissolved and started building up at injector nozzles...I don't know. All i know is this happened to me and I'm doing all I can to prevent from happening again (including doing every install going forward myself). Although I can do my own installs, new gaskets and machine work still adds up.
e85 doesn't pool, it would've evaporated.
Pitting on valve seats is caused by the valve closing on debris- ie dirt, sand granules, etc. it's inevitable.
This is my connection between oem fuel rail and fpr where I let evaporate since I took off my injectors for cleaning and didn't install injectors until head was built. This is dried up and sat for 3 months. And yes, during these months, it rained a lot so moisture was plentiful.
Again, this is what I found on my car. Believe what you want and take your risks as informed as possible.
