I’ve mentioned on here a time or two that I’m a die-hard mouth-to-lung vaper. My favorite tanks for flavor have always been kayfun/russian style tanks. After enjoying a couple of FT Russian 91% and several KFv4 clones, I decided to give an authentic a go so I purchased an KFL+v2. I was very pleased with the workmanship compared to the clones, flavor was as good if not slightly better, but the whistling and hissing of the draw of this thing was MADDENING!! I was very disappointed. I had actually shelved this thing for months when I came to the determination that, by God, I spent hard-earned money on this and was determined to make it work!!
I disassembled the KFL as far as possible, smoothed, filed, sanded every corner, hole, nook and cranny. I then proceeded to reassemble it, held my breath… took a toot… and VOILA!! The Pied Piper had returned!! 
I must’ve sat in my chair for hours mulling over what to try next. I had done extensive research online and found solutions ranging from drilling out the intake hole to stuffing the hole with kanthal, strands of silica in the airflow adustment hole, wrapping the airflow adjustment screw with teflon tape, etc… etc… etc… I’m not willing to try any solutions that are irreversible, so drilling is a no-go for me. Most of the other solutions were marginally successful in stopping the whistling. The silica in the airflow adjustment hole nearly silenced the entire works and I thought I was onto something!! That is until I filled the tank and started vaping away. About 10 min later, what was a virtually silent KFL sounded something akin to a snoring chipmunk!! 
Evidently condensation saturated the silica and turned it into a phlegm flap. NEXT…
I was about at my wit’s end, so I figured I’d let it go for now and see if a solution would somehow present itself when I least expected it. I proceeded to take a long hot shower to refresh myself and try to wash some frustration off of me. Afterwards, while drying out the insides of my ears with a Q-Tip I had an epiphany. I WAS HOLDING THE SOLUTION IN MY HAND!!
Grabbing a handful of Q-Tips, a razor knife, my wire cutters, and my hopes, I went back to my desk. After a little trial and error, here’s what I came up with:
I clipped the cotton ends off with my wire cutters, then cut off about 1/3 of the tube that remained (lengthwise). Keep in mind that, obviously, this only works with plastic Q-Tips and not the compressed cellulose ones.
I then rolled what was left of the little plastic tube back and forth between my thumb and finger until I had formed a smaller tube. I removed the AFC screw from the base of the KFL, and carefully inserted newly created smaller plastic tube into the air intake. It was a tight fit, which I wanted. I then carefully trimmed the excess tube flush with the surface of the body of the atomizer. At this point, I could have either left out the AFC screw entirely, since the tube was covering the AFC hole, but I reinstalled it, if for no other reason than to NOT lose the little bugger…
Then the moment of truth…
EUREKA!!! SILENCE!!!
OMG, my KFL+v2 is now as silent as primer puffs on a Nautilus. No more whistle and NO MORE HISSING!!
Yes, this is how I spent a Saturday… Yes, evidently I have no life… *sigh Hopefully someone someday may find this info useful to them…
Note: Using this method will cause you to lose airflow control, but the draw is perfect for me. If you follow this same method with the AFC screw all the way in, the plastic tube will stop at the screw, allowing you to keep your AFC…