You're talking apples and oranges here. Yes, the originals were pleated but contained farther back in an airbox and pulled in mostly still air. K&N replacement airbox filters (original copies) will probably work fine but their pod style, not so much. They do work, you just won't get the best performance possible out of your carbs. No doubt they flow enough air, it's just that the flow is turbulent around the outside edges when it first comes through the pleats. The problem arises because the intake bell on your CV carb has air jets and an air intake for slide operation around it's outside edge.
The rough air flow to the slide intake cause a phenomenon called "slide flutter", which is just what the name implies. Instead of lifting smoothly, the slide will bounce up and down rapidly. This occurs mainly when the slide first tries to lift, around 4K. This makes the carbs more susceptible to break-up in that range. Now, if you're increasing main jet sizes due to mods, break-up in the 4K range is one of the indicators you look for to tell you your mains are getting too big. The K&N pods allow this to happen sooner, before your mains actually are too big. So, you end up running mains smaller than ideal. You think you did right because you followed the carb tuning indicators, but you've been fooled. The K&N pods are causing the break-up, not the mains.
