I had also read somewhere about turning the end of a cartomizer to adjust the air flow and I've tried it on two different ones and each time it has killed them. I have learned my lesson the hard way.
This is my experience as well, and like an idiot I did my first experiment on cartos that had my 2 favorite flavors in it...argh. It didn't work on the first one so I then tried a second...doh!
Anyhow, for anyone reading, what happened to my cartos is that I had virtually NO draw at all after the "adjustment." It's not like the atty part died, more like some mechanism was closed off so that no flow of air or anything could get through, so in order to get *anything* you'd have to suck like a Dyson vacuum cleaner. And no matter how many times I tried to "re-screw" it back to where I started, it stayed the same.
It's doubtful I would try this again, but I do wonder if I pushed down too hard while using the screwdriver. Probably not, maybe it's just not a good idea for cartos.