I cant find where vacuum hose is supposed to go..

[joelinvegas]

1997 e420 small vacuum switch on front of motor. it has 3 small vacuum ports and 1 electrical connection, the ports are marked 1, 2, and 3. the #2 goes somewhere under the intake and the #3 goes to the egr, the #1 is missing and i cant find where it is supposed to go. any help would be appreciated. I cant find any diagram that shows this for some reason.