Cruising miss (lean)

Can't really go by plug color with unleaded gas.

I'd be checking my ignition. Same ting happened to me once and I had a wire that would touch a header only while I was going down the road. Another time I was getting surging at low constant RPM. That was the junk MPP dizzy that has an advance rate that is way too fast.

I'd also be considering the total timing including that damned vacuum advance.