If it's running good in stock form, don't mess with it, The 250 makes usable power.
Any mods you make will require Re-jetting, and that's usually a 3 month ordeal till ya get it right.
Trust me, the HP gains are minimal compared to the hassle required..
My advice is spend your time getting the suspension set up for your weight & riding conditions- get the bike to stick before you get it to kick..
I might still do it anyway, since i have all the tools, and i can do it myself.... but i dont have a jet drill around the size i want :( so i'll go around to some bike shops to try and find a jet.
I will really do anything for even the slightest improvement in power, as money is very limited (im 14yrs old and dont yet have a job). I just really want a bit more power to be able to keep up with my riding buddies... as it is, my stock bike surprisingly beats an 03 xr250 in a 200m race.
although, takeoff is a little bit slow... and this is what i would like to improve, whilst still maintaining the 110km top speed...