What would be the cost to mill and port the heads (I'm assuming that is where the extra power is coming from)? I'm on a very limited budget, but if it doesn't cost too much I may as well get some work done while the motor is out (need to change out the springs anyways).

As far as cams go, any reason you'd recommend an E over the F? I was looking for a cam with more mid to high end power. F seemed to fit the bill.