Bad gasoline causing problems

My daughter has a 1988 chevy celebrity 4-door. She got a tank of bad gasoline. Since, I have added gas treatment and she has driven most of the gas out. I replaced fuel filter also. Now it is dying and still running rough. It mostly dies when you come to a stop but sometimes it dies while you are going. You push on gas and it lurches forward. Any suggestions for this mother who lives on a low, low budget without taking it in to the shop. My daughter only works parttime. It has 86,000 miles on it so far.