[MikeK]

Im no fan of E10 (AKA 'crap gas') but it gets blamed a lot for boiling/vapor lock issues when the real culprit is the individual RVP (Reid Vapor Pressure) of the specific fuel blend or refinery batch.

Any fuel blend should have a max RVP of about 8 or 9. Adding 10% ethanol raises that number about 1. Atmospheric pressure is about 15 so the fuel does not boil at normal temps if the RVP is below that number.

The real culprit is one of the other blend components- Butane. By itself it has an RVP of 52. It boils at 30F. Put more than 2% in a fuel blend and you will never get the RVP of the blend low enough to avoid boiling at high under-hood temps unless the system is pressurized well above the blend's RVP.

Butane is kind of a refinery white elephant- extremely little market and value. Refiners will try to dump as much as possible in the gas mix without exceeding allowable local RVP's or, lacking those local regulations, as much as possible without excessive tank boiling and overwhelming of modern vapor recovery systems. Some northern climate 'winter blends' may have so much butane they boil on a 60F day.

My suggestion: Try a different brand fuel, from a different refinery. Drain the offending stuff and use it in your modern with a pressurized fuel system. Unfortunately there are no simple RVP test kits like there are to measure % ethanol.