aNj, just adding a VF isnt going to benefit much on stock motors. I agree with powersledder. What sled is that youre working on to improve? Like others stated, work on the clutching and gearing, would be a start - also heads cut is another way to improve snappier power. There are many ways, and how much money youre willing to spend. WL
My neighbor used to say "The speed that thrills, the speed that kills"