I have a 1993 Dodge D250's with a 5.9 Cummins. I have had a little trouble with the vacuum pump and the brake assist in cold weather. Last night it was really cold and on the way home from work when I let off the accelerator I heard a click. the brake warning lights came on and I had to stand on the brakes to get the truck to stop. also when I turn the truck off the engine kind of ran on a little bit. it had never done that before. could this be just a bad vacuum pump. The engine run on was unusual could that also be because of a bad vacuum pump?

 

Sounds like a bad vacuum pump. Have you put on a vacuum gauge to see how much vacuum it's delivering?