1985 Gmc Sierra Truck Been Family Since New Mileage Accurate Engine Runs Top

My truck has been in my family since new. The mileage is accurate. The engine runs like a top, but Im having trouble with the choke. I can pump the accelerater twice and it cranks immediately. However, even when I let it warm up, it boggs down and sometimes stops when I accelerate. Before I start messing with the choke, I wanted to ask for advice and direction.

Thanks
Danny