Brothers 2020 Mustang

Brother has a 2020 Ecoboost with roughly 120k miles. Two days ago it threw the CEL. Misfire cylinder four and P0300. Cleared and next day threw a misfire cylinder one. He thinks it’s just a bad tank of 93 from QT. I think it’s possibly an Ecoboom and he should take it in for a diagnosis. he doesn’t want to take it in for a diagnosis . He wants to do coils and plugs first. Thoughts?