Q: Hesitation on acceleration - 1980 Chevrolet C10 Suburban

Hello I have an issue with my suburban , it have been working perfectly since forever and I perform the usual mantainance I used for traveling once or two ce per month and sometimes in the city to transport big equipment (I'm a musician ). But last week I experienced a hesitation on acceleration when I press the gas pedal , the carb it's a quad , starts quickly and works perfect at low speeds when once I go to the highway and press the pedal down (opening the first to barrels to full) it feels the lack of power and If I opened the 4 barrels accelerates just good as usual . So the problem it's when I opened the first two barrels wide open . I checked the vacuum lines , no further problems with them I replaced them new , also cables , fuel lines , fuel filter , air filter , spark plugs , etc . The problem it could be the acceleration pump on the carb?.

Thanks !!!.

My car has 99999 miles.
My car has an automatic transmission.