Engine misses, sputters and jerks when applying little gas.

I have a 1998 chevrolet c1500 5.7 two wheel drive truck. I have in the last 6 months changed... The ignition coil, plugs and wires, erg valve, Maf sensor, wiring harness and battery. I am trying to fix a miss my truck can't seem to get over. After I put the new erg valve on it seems to go away for a day or so then when I took the truck on a long drive it started in slow then got worse. When I drive the truck it use to only spit and sputter and miss only when I applied a little gas to it, and now even when I give it any amount it spits jerks and misses. I mean it is still drivable, just very noticeable especially when your in the truck and can feel it. Any idea of what it could be?