1992 Oldsmobile 88 Engine runs rough

I've replaced the spark plugs, wires, air filter and vacuum lines. When the engine is cold it runes great when I come to a stop sign or light, etc. But when the engine begins to warm up, it runs rough when I come to a stop, but when I take off it runes smooth through all gears and up until I come to a stop again, then it loapes and jumps (runs rough). Then sometimes it stops for a few stops, then starts again.