I have an E350 club wagon when I put on the brakes the brake pedal will not return I have to lift it up with foot to release the brakes.
I have replaced both calipers and hoses, master cylinder and brake booster brakes work great but still have same problem.

 

Can you try this,
Engine off, pump brake pedal until all vacuum is consumed and pedal becomes hard.
If the pedal still will not return to full up position check for binding of pedal bushings where the pedal pivots. Some penetrating oil should help loosen them if that is the problem.. Let us know what you find..Thanks