i don't have a sigelei but rather a vamo, and i just got a PT2 less than a week ago.
i popped the first coil that came with the kit, so i put in the second coil.
same thing happened to me - if i had it screwed on fairly loose, i got a tight draw. if i tightened it a little more, about the same tightness i use for my original PTs and any other clearo or atty, i got nothing. almost no air at all - i'd really have to suck hard to get just a tiny amount of vapor.
swapped that head out for one i had previously recoiled/rewicked, and all was good.
sounds like a bad head. replace it for another and you should be golden. once in a while you're gonna run across a bad head.
other than that, the PT2 is a phenomenal clearo, IMHO...