92 lumina overheating and stalling problems

okay, so i have a 92 lumina that keeps stalling on me. i took it to a shop and they said it was just the water pump. the overheating was causing the stalling.the water pump does have a giant leak in it but i dont think its causing the stalling cuz it dosent get worse the hotter the car gets it gets better. the longer you drive the car the less it stalls. it feels like its not getting enough gas. sometimes, to get it to move at all i have to press the brake and the gas at the same time then let go off the brake. plus when i put fuel injector cleaner in it it stopped stalling altogether for awhile. plus ive been driing it with the overheating light on for a little bit and nothing has happened. someone please tell me whats going on with this thing.