1998 Saturn SL2 1998 Saturn SL2, starts to die & stall

When I start the car, sometimes it starts normally but on other start up's during the day, I can hear/know the engine is going to die or choke, so I have to put gas to keep idle running. This also might relate when I change gears other than neutral that the engine chokes on a few occasions. I already had the 90K maintenance 4 months ago at the dealership, with new fuel injectors and had the engine check which was fine; the problem had occurred before the maintenance which I thought was fixed. So what could be the problem?