FNG here. I have an '87 2WD 5 speed pickup with a carbureted 22R. Bought it new, it now has 426,000 miles. It has always had a mild lean spot in the carburetion which is now gradually getting worse. The carb was rebuilt 5000 miles ago with a NAPA kit.
It has a mild lean stumble when cruising at about 50 mph. It disappears with any change in throttle position. What change can I make in the carb to richen the mixture at this throttle position(1/8-1/4)?