Identify part '53 V8

I have a '53 V8 running on LPG. Just to the rear of, and separate from, the ABS unit in the engine bay is a black plastic cylinder approx 6" long and 3" diameter. There are two pipes, one connected at either end via push on rubber connectors. They look like vacuum pipes and run back into main engine area. What is this unit and what does it do? Reason for asking is one pipe was not connected to the rubber connector.