brake pedal goes to the floor at start up

With my foot on the pedal, I have a good strong brake while my motor is off. As soon I as I start the engine the brake pedal goes to the floor. I’ve replaced the master cylinder (bench bled it), and have bled the brakes three times. My calipers are on the correct side. I don’t see any leaking fluid at the wheel cylinders or calipers. I do have power brakes. Is there any way the booster could be the problem? Any ideas?

Thank,
Kris