I'd check the PCV Elbow at the back of the intake manifold,
look for a pinhole in the rubber elbow that plugs into the back of the intake manifold. If that's what it is it's a dealer item about 48.00 trouble code to accompany that might be a P-0171 and P-0174 Left and Right Banks running too lean.
A temporary fix is clean the elbow (carefully) then wrap it with thin strips of Duckt Tape about 3" long.
Good Luck and let us know how you did.
Oh and Welcome to the forum.
97 Expedition EB/Cadilac Escalade White/Ghost Flames/22"Boss Wheels.
"Have you done it in a Ford lately?"