Ok, mine was on the line from the vac transducer/ exhaust gas recirculation valve.

Should I put one on the shut-off valve line also?

__________________
"Well, once again, we find that clowns and anarchy don't mix..." - The Tick
'94 E320 ~ Wikel
'87 300SDL ~ Frieda
'87 190E ~ Thurmond III
'84 944 ~ Schrickelgruber
'86 535i ~ Joerg