1988 Lincoln Town Car AC and Heater

when the car is accelerated and the AC or Heater is on in auto mode or manual mode the blower motor slows to a crawl and some of the cool air goes to hot and when on heat the blower slows. I have been advised that there is a possible vacuum leak. I have found a small hose connection that is located by the Cruise control on the driver side that was wide open with no place to plug in. I placed a vacuum gage on this hose and at idle it reads a steady 28. I plugged the hose due to lack of a place to put it. Plugging didn't change much. I will continue to search but any help you can give may shorten my search.

Thanks