I'm having the same problem. The tank keeps filling up with vapor and makes my juice turn dark and taste weird.
Actually, the juice inside a MAP tank oxidizes, which is what turns it dark. It does it for my juices as well, but they still taste great! In fact, some juices which usually need to steep taste better a day or two after I've filled the MAP tank. This isn't happening because of the vapor trapped in the tank, it happens to everyone.
I've removed the top delrin cap and adjusted the placement of the clear piece that fits over the CE2, but no matter how many times I do this it still continues to get vapor inside. The top cap is pushed down as far as it will go. It's sitting right above the wick and I can only see about 1mm of the little clear plastic piece.
Anyone have any other suggestions? I love this thing but I'd love it a lot more if it worked right.
I had this problem (vapor remaining in the tank, after I took a drag on it), but I seem to have solved it.
I put the MAP tank on my ProVari, and screw it in, but just the slightest bit. I then press down firmly but carefully, on the top Delrin cap, trying to push the CE2 as firmly up and into the top Delrin as it'll possibly go.
I then screw the MAP tank completely onto my ProVari, and give the Delrin cap another firm push, to make sure it's snugly in place.
I now turn the ProVari/MAP completely upside down, over a paper towel, and leave it for about 10, 15 seconds, just to make sure that it doesn't leak. It hasn't leaked at all since I started to do this, and I also haven't gotten any remnant vapor remaining inside my MAP tank since I began making sure it's all tight.
My juice DOES still turn dark after a few hours, as I mentioned, but the juice still tastes great, some juices even taste better after a little while exposed to air!
Hope this helps.
By the way... a ProVari with MAP tank is THE combination for perfect vaping, without much hassle, in my opinion! Love this combo!