Rough idle/slight skip

I have a 1993 Plymouth Grand Voyager.3.3 liter.189 thousand miles. The engine runs rough like it has a skip. It seems to be worse at idle but there is also just a slight miss at higher RPM's. So far i've replaced plugs PCV valve and air filter. All of the vaccum lines look good plug wires are fine. How would I know whether to replace them or the coil. I was sure that the skip would straighten out after I replaced the spark plugs but I can't seem to get it to run right.