I had one on the 1.4 fiesta of a similar age.
If you do it will be behind the inlet manifold area
On the Zetec, the PCV system vents back into the back side of the intake manifold. If you look for it, its a rubber elbow about 4" down from the throttle body. That hose has a tendency to collapse and then break. SO with the car running, listen for an air leak by the intake manifold.
from memory few years
symptoms i had was erratic idle and i could hear the air leak