What are some reasons my van cuts off while driving

I have a '96 Plymouth Grand Voyager SE.

I have replaced the computer, fuel filter replaced, radiator replaced, oxygen sensor replaced. Took it to AdvanceAuto it read, "EGR" needed to be replaced. Waiting on payday to replace it. It cuts completely off while driving. It also ''bucks'' at certain speeds. (By that I mean say I'm going 45mph it'll jerk I'll look at the dash board the speed odometer will fall to zero then back up the my speed. All within seconds) Sometimes, recently I'll step on the gas to get onto hwy from my driveway and it will completely shut off. I have to put it in ''N'' to re-crank so I don't get hit if anything is coming. It even shuts completely off while at red lights. My husband changes the oil often, and we just services the transmission fluid. What may be some other reasons it acts this way?