1989 Toyota 4X4 truck During acceleration, there is a point where acceleration stops

1989 Toyota 4x4 truck 100,000 miles. During acceleration, (stock-carburetor) there is a point where no more acceleration occurs, pedal on the floor. Let off gas slightly and reapply acceleration continues slowly. However, recently there is a "bump, " like hitting a small pothole and then I have excellent acceleration. Is the lack of acceleration a function of the vacuum and emissions system, and what is causing the "bump" sensation? Is the "bump" an indication of a serious problem?