/6 when hitting the accelerator...

I'm having an issue with my /6 225 in the 68 Valiant. When I'm at a stop light or out of it, i'll hit the accelerator lightly and the engine acts like its dying out or going to stall. now if I punch it to the floor theres no problem. Does anyone have an idea of what this could be? maybe needs a fuel filter replaced or maybe water in the gas tank and its might be sucking it up. Because after a while it will disappear and the accelaration will be fine and then it starts up again.

Thank you,
Corey S.