Map Sensor Vacuum Line

I have a 1989 E350 Van.

While changing the heater core, I knocked off a vacuum line.
This line begins at the map sensor and travels back toward the top of the motor. It's about 2 feet long with a rubber elbow on the end.
I can't find where the end opposite the Map Sensor should attach.

Any suggestions?
Thanks

Do you have a vacuum diagram?

Kim,

Thanks for your reply.
I do.
It says under the hood that it goes to " MAN" I assume that's short for manifold, but can't find where.

Any suggestions?

Thanks