A bit of reading and a little care and a muffler mod is an easy way to gain 10 to 20% in most cases. As long as you are clean about the work and set the carb up right when you are done it's a pretty easy job on most saws.
Likely another 10% can be had with a light cleanup of the porting, do your homework and it's not hard.
I would not jump into a $1000 saw though without doing a lot of reading and learning and expect to risk nothing andhave a great porting job first try.
None the less a propper muffler mod and good work saw porting together can make many saws cut 50% to 100% or more faster than bone stock.
There is no free lunch though, even a muffler mod will stress certain components of a saw, cooler yes, but the extra RPMs tend to increas internal forces on bearings, pistons and rods, and no matter what if more HP is taken out of an engine stresses and wear in some areas must increase, that's physics 101.
If you get into porting the more you gain in speed and power the more you give up somewhere, with mild work most of the sacrafices are going to be fuel consumption and noise, maybe a little piston wear. Want to go faster yet and wear, reliability and usability will start to suffer more and more, at some point it's just not practicle for a work saw.
