Here is the answer you are looking for. When your slides are closed, the extra airflow does not matter from the open air box, K+N's, etc. The airbox w/lid will allow the same amount to flow through the cutout in your slide, and airscrew adjustment as if it were a wide open airbox. Now if you open those slides wide open, your snorkle has just become a bottleneck. Does this make sense to you or do I need to explain futher?
I am not sure people actually read these posts sometimes, I was getting frustrated reading through your post....