I have heard of folks putting some quantity of 2 cycle oil in their E-10 (in old/classic cars) to cut back on vapor locking. Sounds nutty, but I may try it. It certainly cannot hurt the engine. I'm thinking about 8 oz./half tank of an FJ40. If it makes no difference, then dump in another 8 oz. I suspect it won't help, but who knows.
Colo Springs, CO