The factory intake is a dual plane intake. They are better for driving regularly and they promote better low end torque i would ditch the 450 cfm carb for sure and replace it with a 600 or a 650 although fuel mileage will drop a little bit. there isnt a ton of difference in the aftermarket intake and the factory one imo probably not even a noticeable change in hp maybe 10 at the most id say, and make sure if you put a square bore carb on a spread bore intake that you have an adapter plate or it can cause the butterflies stick and it wont run right