A friend with a '97 F250 had to replace the fuel vacuum relief valve on the side of the fuel bowl. When did Ford delete this feature and why was it there to begin with?
I am not aware of one on my '02 PSD.

Just curious,

 

Yup, right; why is there air in the world?
Your both out to lunch.

Come on, the fuel systems are fuel injection under pressure; where are you guys getting anything about vacuum except at the fuel tank as part of the Evap test the PCM does.
It is illegal the have a glass fuel bowl in the fuel lines of high pressure injection system that can have pressures as high as 90 psi.