Do not use any type of fuel system additives.
The EcoBoost platform as a whole are extremely sensitive to certain things that most people would assume make little to no difference like octane variance and spark plug gap. We have yet to find an additive that is exact enough to endorse for use in the EcoBoost motors. Probably about 40% of our EcoBoost tuner calls are because the driver hears pinging or knocking, and they immediately assume that it is because of the tune. Our 1st question (after years of freaking out on our end of the phone) is did you add any type of octane booster or other additives to your gas? And 99.999999999% of the time the answer is yes. So we tell them to just take it easy until the tank of fuel is gone, refill with the best fuel that they have in their area and then drive the additives out of the system. The other 50% is why is my car not running right after installing a 3 BAR MAP sensor. The last 10 or so % are calls asking if we have a faster tune because one of their buddies at work has a new Hellcat or new Z06.