98 cavalier stalling

I have a problem with rough idle and stalling at idle or when coming to a stop. The car will start right back up, but hesitates when starting out.
Removed EGR valve and cleaned it, stills stalls. The PCM finally thru out a code when it stalled last, code was system too rich. Would appreciate any input. Thanks

well. if your running to rich. check your o2 sensor