Dumb, lazy question here: can you run the KFL19 without the little nylon airflow control thingy installed? I'm sure this has been asked and answered several times already all over the forum, but I'm finding it too overwhelming to search today.
Yes, you can. In fact that's how our Qorax Stan runs his.
See his most excellent video on Page 1, it's in Bronze's first post.
Authentic Svoemesto Kayfun Lite - 2019 & 2021 Version
If you decide to run yours without the nylon grub screw make sure your wick shoulders are not touching the center AF block. If they are, you run the possible risk of juice flowing onto the block and down the AF into the 510 assembly of your mod.
On all my RTA's I make sure the wick shoulders are away from the center AF block. Here is a photo of how I do it. It's the Tripod deck which has a similar design much like all the modern Kayfun's.

Wick shoulders are away from the center AF block.
Qorax Stan had no problems running his without the grub screw.
Alternatively... you could leave it in and back off the grub screw for more air. With, or without, the AF grub screw you'll still get a maximum of 1.8mm AF.
Don't back the nylon grub screw out too far or some mods may not see the atty. I knowz this from experience.