Distributor Problems, Missing on Cylinder #4 Options

[warrenoliver]

I just returned from a long weekend trip with some other PCA members. The weather was beautiful and we had a great time. My car did not cooperate. I have a 73, 2.0 with FI and Pertronix Ignitor ignition. I have had the Pertronix ignition for a couple of years now and I have had no problems. The problem I am having with the car is that initially it runs great while the engine is cold and while it is warming up. Once it is warmed up - about 7-10 miles, on country roads, it begins missing badly. The miss is not consistent and seems to get better on acceleration. When I come to a stop, the engine idles very slow (200-400 rpm) and sounds like a John Deere tractor.
I put a timing light on each of the spark plug wires and found cylinder #4 is misfiring badly. I thought maybe the wire was bad so I switched it with another cylinder and found that #4 was still missing. I had an old distributor cap and put that on thinking maybe it was a cracked distributor cap. The problem stays with cylinder #4 with both caps.
I am now thinking it must be either the rotor or the electronic ignition module. Tomorrow I will try a different rotor.
My question is: Does this sound like the electronic module is going bad? When they go bad, do they cause this intermittent miss? Any other ideas out there?

Thanks.

Warrenoliver