when I am driving down the road, the pedal feels fine.
Then when I stop at a light, and try to pull up a foot or so, it goes extermely stiff like the booster isn't doing anything.
It does this over and over.
I took the vacuum line off at the booster while it was idling and it had strong vacuum
any ideas?

 

yeah, your booster is on it's way out. had the same thing happen to me, on my first car, in the underground parking where i lived. almost went right through the garage door, thank God for a working parking brake!