There are so many possibilities..
EFI so probably not vapor lock.
Agree with Bud on ign. module and this would be my first guess. They are VERY prone to failure and even if it's good, I would carry a spare.
Could be rubber fuel lines destroyed by our new corn gas and it's sucking air.
Could be a bad fuel pump even though you can hear it. Sock for FP may be clogged.
Eng sensor(s) could be failing.
Cat converter could be clogged. (I would replace the 02 sensor in it even if it runs fine).
Injector clogged.
Vacuum leak.
EGR sticking open.
When it does it you need to check for the basics: Spark and fuel.
