Brakes not working right

Awhile ago my 89 E350 with the 7.3 IDI started getting a very stiff brake pedal...meaning both feet on the pedal and pushing as hard as my 200lb frame can to come to a stop. Lotta guys suspected brake booster took a crap...took it into the shop and had a new booster installed. 1st day brakes were better, not quite like i remembered where a slight touch would send you through the windsheild, but pedal feel was alot better.

Next day it started going south again needing ever increasing pedal effort to slow this beast down. It's now at the point i deemed it unsafe/road worthey for use, so stopped and picked up a vacuum pump for it since i was told these go bad too...though C6 tranny shifts like it should and selector valve for HVAC stuff works great though i know they dont take much for vacuum.

So, does that sound reasonable, the belt driven vacuum pump finally took a dump or is going bad? I have no shop to work on this thing so everything gets hired out to the mechanic shop or i'd diagnoise it myself, and when i say i have no time to mess with it, i dont, but this is our traveling tool bin so it's needed almost daily for work since it houses all my construction equipment, hence waiting for an opening to take it in and just nursing it until we have somethig else planned for the day.

Lemme know