rough idle on 94 v6

daughter has 1994 mustang v6. at idle the car sounds like it is about to die. performance is ok while driving, but upon stop or in park idle sounds like it is dying. the head gaskets replaced several months ago with new plugs. no new wires. i have checked for vacuum leaks, none i see or hear. checked pcv valve, air filter, and cleaned iac. the exhaust smells very rich mixture. i am at a loss, will try new wires this weekend, but looking for other thoughts or ideas. thanks in advance.