You first item to check would be fuel filter. Take note if you have substantial air leak just prior to intake between air box tube to carb intake it may cause inefficient backpressure. Worse yet if your running a performance intake filter on oem carb it may cause same issue. Lack of backpressure messes up the fuel/air ratio and causes severe bogging/starving of engine to the point of bringing the engine back to idle or stalling. Worse scenario is if you take it on a test drive without the airbox on it for some other reason this is a perfect condition for bogging. It is designed for a designated amount of restriction.
