I say porting your cylinders is the most affordable way to get more power out of the bike b/c you only have to spend money on porting $300-$450 depending on who you choose. Going with a 4mill motor is going to put you more in the $1500-$2k Range based on if you do your own motor work, you need to have your cylinders specifically ported for the 4mill stroke. A 4mill is going to have a lot more torque and more all-around power than a stock stroke motor. So if your wallet permits over a $1k build, I would definitley go with a 4mill Motor that will put a huge smile on your face.