Jam on Brakes from idle speed then engine dies and won't start.
 

Alright so I went to cross a busy 2lane highway and when I went to go a guy came over the hill real quick on the highway so I jammed on my brakes (idle speed) and the engine dies, and cranked like 5 times before it would start. What may cause this? It happened a long time ago too but I thought it was just a fluke thing

What does your truck typically idle at? It's possible that the volume of air from the rapid & full application of the brakes was enough to kill it due to low idle speed.

Usually idles at about 500

500 in gear, fully warmed up? That doesn't sound too bad. Could be higher.

When you press on the brakes, can you hear air rushing in around the brake booster that would indicate that there is a vacuum leak when active. Shortly after shutting down the engine, pull the check valve out of the front of the brake booster, is there a rush of air into the booster?

I'll check it out in the mornin when there's some light and not pouring down rain, i'll update it when I look.

*Update,

No air sound to the brake booster pressing on the brakes, and when I shut off the engine and pull off the vacuum hose off the booster air rushes in, so that would indicate there is no vacuum leaks correct?

Try this next. Let the engine run for a bit, then shut it off. Have someone apply the brakes while you listen at the booster. But yeah, it doesn't sound like the booster is your problem.

My Jimmy always acts up when it's raining hard outside, is there something that could get wet that could cause this? Dang newer vehicles lol