box stock engine, grab the best pipe you can afford, get some nice reeds, air filter for your environment (sand or dust) and jet that bad boy! There is more to it than chasing a port job. I was there once. Had to get kicked in the balls a few times to realize sometimes you just want to ride the damn thing.
If you're after good work. Ice racer, FloTek, Tony at T&R, Tudors still does some work on the 250's, surprisingly enough there is a large following if you can find them.