gas problem

my 93 corolla act as if it has bad gas in it after i feeled it up 2 weeks ago. it act as if it going to cut off when i stop at a traffic light. after i refeeled the it still does it. i refeeled at a different the second time.it does some times when the car is idling in park. sometimes it hesitates when i'm going about 50-60 mph. i changed the spark plugs a couple of weeks ago. i didn't change the wires though(tight on money). could it be the wires or is it the gas or the gas pump or gas filter. could some one please help.