Missing at low rpm's
 

I have a 2001 Astro w/4.3 with 213k miles, and it has recently been misfiring a low rmp's or light acceleration.

I have changed plugs, wires, distributor cap, button, fuel filter, fuel pump and treated it with Seaform, twice, directly into the pcv vacuum, as well as ran a can through the gas tank.

All of these parts, being at 213k miles, needed to be replaced anyhow, because they were in poor condition, but after this fuel pump replacement I am starting to get frustrated and at a loss.

My parts guy hesitated to offer up anymore suggestions and suggested a mechanic to me, but thought the next course of action would be to replace the distributor, thinking that the stator might be bad.

What confuses me is that when I start to accelerate it wants to stutter, but if I get into the gas or am at highway speeds it runs smooth as silk.

Any input or suggestions would be greatly appreciated!