Eric gore will port your bike right, he is across the pond now very expensive and a long wait. He used to be the best (and to some ) still the best at 2 stroke port work.
You can advance the timing and a whole range of things but cutting the metal up. He will port it for your style of riding rather than, ITS PORTED GOTTA BE BETTER.
If you want top end, bottom end, mid range ect. Sealey is pretty good to and on this side of the world.
Not that i am a expert, but if i had a jug and wanted to get some work on it. I would ride the coat tails of the 250r guys a bit, and see who's doing there port work.
Curtis sparks is about garbage from what i been told (allthough the hold retail resale) There is some top notch guys that really know what they are doing.
If you really wanted to get something done, post around on the 250r sites. You will find alot help. (lots more 250r's) but they still are a 2 stroke.