The JG is a more aggressive port over the ITR and the Skunk2. It has the single butterfly just like the Skunk 2, that is what makes the Skunk2 different from the ITR. The Skunk has the same bore as the ITR. So for such small differences, I would either overbore a Skunk2 and save the money, or just bore the ITR and don't worry about having 2 butteflys instead of just one.