Stiff brake pedal in traffic
 

i have a 94 dodge ram 2500 cummins and when i get in towm where i have to hit the brakes over and over sometimes they get stiff and if you put truck in nuetral and rev it they free up. i just pulled vacuum pump off and cleaned any ideas?

idle is set too low or vacuum leak.

truck idles a little above 750

shotty booster system, something is leaking or not creating what it should be

Check for a leak in the vacuum lines, booster could have a internal leak. I had a little leak in my line and hardly any brakes.