If you wanna take the cheap route, get a K&N airfilter, take off the airbox lid, use "engine ice" coolant, get some hotcams, change the oil to a full synthetic. and i would change the exhuast to a full. And the reliability of what i named is top knotch but you wont gain 25 hp off what i named, but enough to feel a big diffrence.

BTW: the hotcams and the sprocket mod should be pretty good together!!