The K40 (or at least the version I have), has a pretty insufficient / badly designed ventilation system. It features a fan that just barely moves air, and a metal shroud that is supposed to direct the fumes toward the fan but unfortunately blocks the working area by about 1 inch (the working area is not very big in the first place mind you).
So there are two issues needing two solutions. (Duh.)
For the fume shroud, I attempted to cut it down with a circular saw. It almost killed my hearing and barely dented the shroud. (Kudos for using 1mm thick stainless steel, my K40 manufacturer!)
Time to design a new shroud and 3D print it!
Model is here.
Getting some M4 metal inserts in (I used this set of metal inserts on Amazon)
Now it works better!