u/Round-Working-8962

2016 Transit 350 gas turbo with 128K. When releasing the throttle pedal after accelerating, the brake pedal applies itself firmly; cannot hold it back with the top of my foot. If you immediately accelerate, it releases itself. “Service Brake Booster” comes on the screen. Replaced angled vacuum connector with new check valve; no change. Booster? Booster vacuum sensor switch? ABS? Thanks.