96 Cutlass Supreme w/ Rough Idle, but drives good

96 Cutlass Supreme 3.1L drives like a champ but when idling it will drop to about 500 rpms and the engine runs rough but doesn't die. Checked codes at an auto parts store and it had P0300 for Random Cylinder Misfire. I have changed all of the spark plugs and the Mass Air Flow Sensor, then I cleared the codes but it still does the same thing.

Welcome to AF. This can be caused by dirty injectors, a slight vacuum leak, low fuel pressure, addt'l diagnosis will be required. Rough idle is a catchall for many possibilities.