Rough Idle - Running Rich.....

I have a 91' corsica. as the title says it has a rough Idle and is no longer running rich and I cannot figure out why it has a rough idle. I have new plugs, wires, air filter, air box, water pump, vac. hoses, brake booster, and I have installed a new pcv valve. Any ideas on what I can do to fix the problem? Overall the car runs strong with few other mechanical problems.

Thanks