The padded hose from the PCV valve on the left hand cam cover over to the throttle body plenum, maybe? Often the rubber elbows at each end can leak or become soft and collapse. The PCV valve itself should be replaced every 80k Miles.

I can confirm the Motorcraft part numbers are:
PCV valve: EV-261 (2C5Z-6A666-AA)
Hose to Throttle-body: KCV-240 (2L2Z-6A664-FA)

Unsure of MGR numbers, if thee are any.

David