This is interesting because several people told me muffler mods don't help a whole lot on these saws since it's pretty much an empty can(which it is...).The muff mod and tune REALLY wake up these little saws. A good little port job is even better.
Sure you can allow more room for exhaust by extra holes, but that's about it.
I did some work in the air box. Removed a bit of a flange restricting air under the plate that covers the entry to the carb and opened the muffler a bit. I might do a bit more to the muffler after reading your comments.