I have a 1989 Cadillac Deville with an idle/.

I have a 1989 Cadillac Deville with an idle/start problem. I have followed some solutions and this is where I am at now with the problem. If I disconnect the vacuum line that runs from the EGR Vacuum Solenoid to the EGR valve, the car will start and idle ok. If I connect it, the car is very hard to start and does not idle at all.
With the vacuum line disconnected and engine running at idle, any vacuum applied to the EGR valve will cause the engine to stall. Also, at idle, there is vacuum present at the EGR Vacuum Solenoid that supplies the EGR valve.

So far I have replaced the MAP sensor and the EGR Vacuum Solenoid with no improvement. I checked for codes and it shows a 'F-13', 'F-15' and 'F-32'. No error codes though.