Its the design of the base on the Protank. Its hard to explain how the air moves
through the base, but if you make the holes bigger it does help.
I don't think many will do this, but if you're bored and a bailing wire type.
For the 3 small holes around the 510 connector. I opened them up with a #59 drill bit.
The connector base in the replaceable coil. The part that contacts the battery. I pulled it out and opened the hole up with a #50 drill bit.
With (3) #59 holes and (1) #50 hole, the same amount of air should be able to flow through. (3) #59 >/= (1) #50 in area. The air has to come in through the 3 small holes, then around the replaceable coil and up through the hole in the contact part of the replaceable coil. Once I opened up the 3 small holes the restriction is now where it has to flow around the base of the coil. I think adding a 4th hole would improve it, but I didn't want to do it because with 4 holes if I ever drop the thing it will probably snap off.
However, just doing the holes made it quite a bit better and now my coil doesn't clog anymore.