Im thinking that the heat caused by the stock bulb is the main reason for the fogging. I would like to try LED's and close off the tube completely. If not I may install one of those fish tank filter things that bubbles (Or make a silica filter) from one of the silica cylinders found in medicine bottles.

the led bulbs i had in my machine the headlights still fogged up and my vents r in the cab of the machine up buy my head.and you could not see were you was going with the led bulbs sylvania silverstar bulbs are working out really good and with the heat from them seems to be helping with the fogging problems.

Just pay close attention to the power they draw and check your headlight lenses make sure the extra heat isn't hurting them.

i run same type bulbs in my vehicles and have not had any problems there but i will keep an eye on them and let you know.