It is the Fuel Pulse Damper and it looks very similar to the Fuel Pressure Regulator on earlier trucks. Pulling the hose from the FPD does not change the rail pressure.
A Mechanical Returnless Fuel System like the one used in a 98+ Ranger has an inherent problem with pressure variations in the rail caused by injection events. The Fuel Pulse Damper is tuned to help maintain a more consistent pressure throughout the entire rail.
The vacuum hose is just a failsafe measure intended to capture gasoline if the diaphragm in the FPD were ever to rupture. In normal operation, it does nothing.
Here is a comparison of a FPR and a FPD. These happen to be from 5.0 Explorer V8's of 2 different years - Ranger EFI is similar.
Fuel Pressure Regulator (Return Fuel)
Fuel Pulse Damper (Returnless Fuel)