1998 Chevy Truck Won't start

Have a 98 chevy 4x4 having starting problems. Truck had fuel pump replaced about 6 weeks ago. It would start then but if you kicked it down in passing gear would spit and sputter and miss and pop until you let off of the gas some. Has ran fine since pump was replaced until last few days, now the truck is hard to start, cranks over and sounds like it is going to start and eventually will after almost running the battery down, and sometimes have to boost it but eventually starts. Sometimes it backfires through exhaust and sometmes when you stop cranking it surges and sputters back through the intake. Once it starts it runs fine and will start the rest of the day until it gets shutoff for 3-4 hrs then its the same problem. I have been told by several it may be the fuel pump again but the backfiring and other leads me to think its in the timing. You can hear the pump run when key turns on and it pumps up and stops and then after cranking awhile it will be running again. Have been told that these fuel pumps are bad to cause problems just wondering if it could be something that someone else has experienced and could share some insight on the problem. Thanks