Here is my curiosity...
The roughness manifests itself by trying to hold RPM's at 2k and it flutters around a bit but at 3k perfectly smooth.
Previously have run a can of Sea Foam
Now try a 1/2 can of Berryman B12 in a 1/2 tank off fresh/clean fresh fuel. Take it out for a ride, high gear, low speed, so you run the engine in a lower RPM. 1.5-2K approx. Around the city on flat ground. This way you go through all the rpm range. Let sit over night, and repeat.
If it improves, repeat the carb cleaner. If it doesn't clear up fully, but is better. Do the same, but with Techron this time. Then just go out and enjoy. Use Chevron with Techron for gassing up. It should get better and better.
If not. Research carb rebuild/cleaning.
I feel you ports a plugged, and the heavy doses of carb cleaner should do something. Seafoam will work for some, but not all, of the cleaning.