Where does the oil in the vaccum line come from?

[luckys420]

1980 300 td with a later model engine and turbo, i think it said 617. somthing on the block
after doing many searches i could not find the answer
so here is the problem, oil in all ACC vacuum lines, oil in vaccum line at the ignition, but not at the fuel shut off valve, no oil in brake booster line, locks just recently stoped working, engine shuts off slowly( but i by passed the ignition and it shuts off quick) no suction to the black line that turns on the heater valve. wher does this oil come from and what do i need to do to fix it?
i inspected the vacuum pump and could only find one line coming out of it, it is on the top about 1/4 inch and metal, i figure this line does the suction, so if the pump is bad where does the oil come from.
any help or suggestions on what to look for would be great. thanks
lc