If you dont run through mud.. I'd get rid of the air box and go to some K&N pods.. or if you do ride mud. get a pro-flow kit and get rid of the lid.. that should free up some power. Also could get a adjustable timing plate to bump timing up a bit and like you said, get a cool head with some 21cc domes to bump compression up ( That will still let you run pump gas.) . Also I didn't see reeds mentioned, If your still sporting the stock reeds, a good set of reeds will help out too. Porting is going to be the best bang but, you still got some to gain before you pull the cylinders and these mods would really help compliment the port job.