If you’re tuned on winter, it’ll get LEANER when you add summer blend. How much…it’ll vary.
The Fix?
Run an ETHANOL CONTENT SENSOR, get tuned on E78, and you’ll be good to go. I’ve got another fix in the works but we want to research it more before we tell people and it does not work. Regardless, getting tuned on E78(ish), is the way to go.