Hi, after taking everyones advice, I upgraded from a cheap cig look-a-like e cig, and got a totally wicked tornado-t (ego c) kit which is totally amazing! I upgraded it 5 days ago with a tw 3.5ml dual coil cartomizer tank which until today, worked fantastic but for some reason, its started to get harder to pull on when I take a drag. I can't see no obvious changes and it's not leaking, and it still gives me lots of vapour but it's harder to achieve as you need to drag harder.Any ideas? Thanks,Chiller.