2002 Ford F-150 Frustrated

Been having little problems here lately, can u please help me out? Just fixed a trans problem, now when I'm driving truck seems to drive fine but say you pull up to a red light and your just holding your foot on the brake pedal, the truck starts idleing very rough, does not die, but literally starts liberating and like hopping or gasping for air. Imagine sitting in a bad ass hot rod while idleing real low how it kinda hops from side to side, or like sitting on a real low idle Harley, that's best I can explained it. What would cause this now?