I just tried playing with the grub screw for air control. The only way I got the whistle to stop was by tightening it all the way in..so, it goes past the little air "tunnel" and up into the body of the Lite. Anything towards the bottom causes the low whistling sound. The draw is very similar to the regular KFL's that I have in the position that it is now. Works for me! Let me know what works for you when you start using it.
I remember reading in this thread that someone who had a whistle dismantled the KFL completely, and found a bit of metal shaving in the air hole...the one that is the center pin. Another simply turned the center pin a bit. It's not meant to be adjustable, but apparently you can turn it just a tiny bit and perhaps diminish the whistle.

