The hoses that are plugged in my pics are the ones that hook up to the air cleaner when it is installed........there are 4 of them total I believe.
The hose that connects to the diaphragm by the throttle cable is the "Idle-Up" diaphragm that increases the idle when the A/C compressor engages. That hose on the diaphragm runs over to the pass. fender to one of the vacuum switches and when the A/C compressor engages, that switch opens to let a vacuum signal "pull" on that diaphragm and that increases the idle slightly to offset the drag that the A/C compressor puts on the engine when it's idling.
You must be talking about the "Vacuum Advance" that is mounted on the distributor. It is routed a little strangely........look at these pics and follow the white marked vacuum hoses....