Car keeps dying when you give it gas?

i have a 1992 pontiac grandam. i just bought it for $700 about a month ago. well it sat for 6 months before i drove it home (100 miles away) it was great on the way home. but after i took it to get the oil changed it would die almost everytime i gave it gas. it would sputter really bad if it didnt die. well my dad found that a va line was disconnected. well we replaced it and it ran perfect for about 2 weeks, never died once. well now it dies and sputters at least twice when i take it to work (just across town) it seems to die when i have to stop for long periods (like to wait on traffic) then give it gas, or if i have to give it alot of gas, like to get up a hill. does anyone have any clue what might be wrong? i have almost no knowlege with cars so i have no clue