I've seen that same stuff many times on alcohol powered dirt cars injection and intake and anything aluminum that gets near methanol, and it is then left to sit.
A good alky fuel stabilizer will help. Most Sprint car owners "pickle" their Hillborn style injection with Wd40/Marvel Mystery Oil/inser fav oil here... after races, the Methanol attracts water and will badly pit aluminum in a very very short period of time, like a week!
Remember E10 is a min value, I've measured E10 at 18% several times..
Easy way to a dq at the track is un checked pump gas.. IN fuel limited race classes..
My drinking club has a motorcycle problem....