I'd change the wires too. Have you looked at the plug end that connects to the coil?
If you take the wire off a coil, any coil, and look down inside the boot, I think you will find that the metal termainal on the inside is rusty. All of mine were like that when I got my car and I put new wires on before I had a problem with it. I did have similar problem in my 86 MonteSS with the same symptoms that you described and it was the plug wires.