When E10 became an option at the pumps here in Nebraska in the early 80's it caused quite a bit of vapor locking and stalling at stoplights in the summertime but then later w the intro of fuel injection and carbs becoming nearly extinct it became a non issue. Some eng setups are much more susceptible than others and the ones that are it is severe and a real pain. Any way you could get the E10 all the way out & toss in several gallons of non alcohol fuel of some kind (maybe some racing gas ) to confirm or deny that that is the prob. Changing the intake is not the solution imnho