There was a vacuum leak that persisted until yesterday. The cold weather (-20C) finally made the power brake booster "internals" harden, become less flexible.... and the leak was evident when the vehicle was turned off and a slight hiss could be heard for several seconds coming from under the dash. There it was! Getting a rebuilt booster from a jobber for about $88 and installing it for about $85 solved drivability problems.
Now to perhaps solve the hesitation upon acceleration by looking at the accelerator pump (carbed 1984 2.2L engine)....
Ken, Canada