The master cylinder applies itself due to the brake booster. Replacing the brake booster will fix it, but it can also be fixed with a simple mod to the adjuster nut behind the master cylinder. Either wind the bolt in 3mm or put 2 washers between the master cylinder and the booster. Also machine your front rotors as the will have DTV (Disc Thickness Variation) due to the brakes applying themselves. I worked at a Ford dealer from 1998 - 2010 including 4 years as a Master Tech until I recently opened my own workshop.