Help Motor doesnt run right.

[ryhan87]

I just bought a 72 Gmc 1/2 ton, but it wont run right. It has the 250ci I6. With a single barrel factory carb on it. It idles pretty good, a little rough but not bad. But when you give it throttle it coughs and backfires and hesitates. But if you give it full throttle it will rev right up without any problems. On the highway i can get it into fourth gear but its like it has no power. I can get about 105km/h out of it but i have to hold it right to the floor and it burns gas like crazy. Im not an expert on carbs but i think thats the problem, does that sound right. Also it has a new cap, rotor, wires and plugs however im not sure if the points are set up right. I have tried pulling plug wires off one at a time and it seems to be firing on all cylinders and i cant smell unburnt fuel so i think thats fine.