When using BoostMAX (BX-6000-20-16) on 2015 Ford Focus ST with 2.0L EcoBoost engine, it is highly recommended you set the control knob at 75% when using 93 octane fuel. With the control knob set above 75%, the vehicle ECU may sense overboost sending the vehicle into limp mode and requiring a key cycle to correct the code. When using fuel below 93 octane, we recommend setting the control knob at 50%.