Signature 600 chuffing

[Creek]

So running on the individual cylinders, they would all keep the engine running. However, idle speed would drop from 730 to about 500 and then ramp, recover some rpms then drop again. It did this on all cylinders except #2, it didn't lose any rpms. The single cylinders sound really strong but the rpm drop has me curious. Weak injectors? I get 8+ mpg hauling light at 60mph. The lifetime engine load data said 14%. Don't sound like much of a load.