92 Maxima Putters and sometimes even no gas sometimes

I have a 92 Maxima DOHC but the problem: Its putters really bad only while on the gas or sitting still. When decelerating the car is normal. It starts right up everytime. Sometimes while im driving down the road ill be on the gas and all of the sudden I have no gas. Ill put it to the floor and nothing but car is still running and after a couple seconds it will just start going again. Sometimes the car will even stall for no reason while im driving. The first time any problems occured i was driving and was making a left turn behind somebody that was driving extremely slow and it just started puttering. The first day the car stalled i couldnt start it for about 20 minutes untill i got a bar and hit the bottom of my gas tank and gave it a little gas before i tried starting it and it started right up.I replaced fuel filter,spark plugs,oil and oil filter. I just ordered a fuel pump but not sure if that is even the problem. Anybody have any suggestions where to start?? Somebody please Help me.