s10 Backfiring

I have a 1991 Chevy s10, 4 Cylinder. Sometimes when i drive my truck, usually after it just has started, it starts to backfire and it feels like not enough gas is getting through when i try to accelerate... I was told to replace the fuel filter, did that.. nothing has changed. I have tried Fuel Filter Fluid but still doesnt work. ANy Ideas?
Thanks,

Mike

Usually backfiring is due to timing or lack of spark (so when so much fuel gathers in the system and it finally does spark it backfires)

Check your timing

Do a tune up (plugs, cap, rotor, wires, etc)

Look at your injectors while running. They should be spraying a nice cone. If they're dripping at all they need to be replaced.