high speed miss

[Standing Elk]

Just curious what you guys think before I start changing parts. Got the A all serviced after its long winters nap. Checked and set the point gap. Two of the lobes have always read .018" and the other two have always read .022". Nothing new there. I set my point gap with a dial indicator with the distributor removed from the car so I know exactly what the gap is. I then set the timing to be correct using a test light just like I have done forever. Yesterday I took the coupe out for the first time this year. Started and ran very well at lower speeds like 20-30 mph. But when I got up to my normal road speed at 40-45 mph I could detect a miss. Sometimes it would get worse and then get a little better for awhile. I always use non ethanol gas and it had fresh fuel in it yesterday. It did not act like a fuel issue. I do have the newer modern type upper plate in the distributor. So any ideas?? Maybe a bad plug?? What do ya think? Thanks