Intermittent Engine Stalling '01 Windstar

My 01 Ford Windstar SEL intermittently stall particularly when accelerating. I'll just turn off the key, shift to neutral and restart again. When running on constant speed it never happen, only when I step on the pedal hard enough. But if the car is not moving (neutral) even if I step on gas hard it's okay. No CEL message. NO error code in OBD II. Cam position sensor, Coil, Fuel filter were already replaced. I tried almost everything, clean MAF sensor, put injector cleaner, change to premium gas, still stalling happens. Could it be the trouble in PCM? Please help.