I have the double diaphragm pump, you cannot see the second rectangular plate which covers the second diaphragm and valves because it is opposite to the top cover. I believe you may have the double charles only because you say you have a line going to the air cleaner. I have a hard plastic line which I believe is a vent line going to the air cleaner, a hard line the same size (black)going to the brake booster, and a small gray line that feeds everything else which is pushed on with a piece of rubber tubing.
3 hoses total.
The single diaphragm is quite rounded and it only has two rigid elbow vacuum lines coming off of it. Both are the same size, and attached with nuts, there is no feed line to the air cleaner. 2 hoses total.
The piston vacuum pump has one hose.
All of these pumps were on W123's
What bother's me Charles is, have you checked the two vacuum lines for oil? It is possible you have a leak at the injection pump or transmission which is sucking oil into your vacuum pump.
Please check these hoses for oil and report back, it can spread very quickly through every vacuum hose, and you will have to replace many components.