I just got a Kanger Protank (like in the last 20 minutes) and I LOVE it! However, I do have a small problem. There seems to be no resistance on the draw. Is this normal? My other tanks require me to put a little bit of effort into drawing vapor from them (like a cigarette or cigar only not quite as much) while the Protank is as effortless as breathing. Definitely not something to keep me from using it or dissuade me from buying another one, but I wonder if it should have some resistance or if I put it together wrong somehow.