I just grabbed the one I could find on Thingiverse, as in why it's linked. Testing to see how it does, currently the point is to test if the print itself will hold up, can worry about stuff like that later. Free printing after all.Very cool that you can make the venturi any way you want. So why'd you make it so small? Might as well just have a round hole punched straight thru to the carb like so many cheap ones out there.
Should flow out to the edges of the adapter, and accelerate the airflow as it travels in smaller and smaller to the carb. Take a look at the picture of this random one from Amazon.............
Amazon.com: 212cc 6.5 Hp Predator Air Filter with Gasket Adapter Intake Kit for 6.5HP Honda Clone GX160 GX200 Go Kart Mini Bike : Automotive