Dr-X wrote:but then wtf do I know about 4age's?
Yeah pretty much that.
I'd go for the one that's slightly bigger than the inlet to your pelnum chamber - or the same size at least! From memory i think 3 inch might be about right for those so thats what i would run with!
For intake you want least restriction - think of it like a turbo, you go with a bigger one to get more air in at the same psi right? Well with a na your trying to get more air in at the same vacume level, because that won't increase but what you can do is increase the volume.
More velocity means that you haven't increased the flow at all, more like reduced it but made it go through a smaller hole so it's moving faster!