Your 86 turbo should have a vacuum pump down under the front on the right side. On mine when you turn the key on it will run a few seconds. If there is no leaks it will stop. I find this is a good easy way know if you have a
leak free system.
The vacuum line that runs from the engine bay into the cabin is to supply vacuum to all the actuators in the dash. These are what open the various doors for different vents, air mix, cabin/outside air.
I also definitely have a vacuum leak that goes from the cannister through the firewall, and then somewhere up under the dash. I think it is for the AC. That would explain why the AC does not work. The AC was overhauled about 5 years ago, but the compressor does not kick in when i try to use AC. Also, I can hear a hissing type sound that seems to be coming from the fuel pressure regulator, or at least near it. Is that normal?
You should find where the leaking AC vacuum attaches to the intake and cap the intake connection to stop the leak.
The fuel pressure regulator (FPR) should not be making any noise. Detach the vacuum line from the top of the FPR see if you can find the hissing noise source.
The vacuum line attached to the top of the Fuel Pressure Regulator runs over to the Fuel Pressure Solenoid (FPS), drivers side of engine compartment, and then another vacuum line runs from the FPS back to the intake manifold. If there is a leak in any of this, the fuel pressure will be to high and cause the engine to run rich at idle. All of this can be bypassed with a short 6" piece of vacuum line from the FPR to a port on the front of the intake plenum as a test.
I will check everything you mentioned and find the leak. After changing the fuel filter, distributor cap and rotor, the car worked somewhat better. I changed the plugs yesterday and it solved the missing. The car now works great. Now I need to find the vacuum leak