samsaridinc1500

So my truck (1996 c1500 5.7 2wd) started doing this just now- When I started it the break was pretty stiff, like I didn't have the truck running. When I put it in Drive it idled down to about 400 rpm's. I had to drive it back home from where I was so I went ahead and took off. As long as I'm actually moving down the road at a decent speed it doesn't seem to have a problem, but when I go to stop I have to basically stand on the break and then when I eventually stop it's died a couple times. One time I put it in N just to see if it would idle a little easier (it also started idling at about 1200 rpms, normally about 600), and it didn't seem to help. I left it there because it was also kind of jumping around and I didn't want to shoot forward. When the light changed and I put it back to D the rpms shot right down to almost completely dying out. I had to do this a few times and it DID completely die a couple of those times.
I have no idea even what to look for here. Part of me wants to say something electrical, but I really don't have anything to base that on. I just replaced the tps, but even if that was bad it wouldn't mess with the breaks like that.

tech2

just guessing here but is the booster leaking? After the truck sits for a while, does the booster still have a vacuum reserve for 1 or 2 brake applies?