1994 Chevy Silverado hestitation

After my truck warms up or drives over 5 miles there's a hard hesitation like its starving for fuel or too much fuel when I step on the gas pedal in overdrive but when I let off on the gas and cruise it seems fine but when I just push down it starts to stumble but if I put in 3rd it seemed to go away but today when I was driving it it was stumbling in all gears now. I replaced the fuel filter about a month ago and the problem seemed to go away but now it started again. My haynes repair book says its acouple of things timing is one of them or the injectors might be dirty and need to be cleaned or the fuel pump is going bad any help would be great thank you for your time Tony