1989 Chevy S-10

[Tamie]

This little truck has been the greatest with the exception that I can not figure out this hesitation that causes it to buck like the gas line is clogged, yet you can mash on the excelerater and it will go away. The gas filter is fine. Had to put in a head gasket, and a modulator 2x's. I've checked the lines to see if it was sucking air. I'm just lost. I'm wondering about the choke on it, because colder weather seems to cause less problems with this. Any one with any suggestions, I would appreciate. This truck runs smooth except when this happens and is great on gas milage, uses no oil. HELP!