The air filters for the 981 Cayman (and boxster?) are long tapered cones. They can fit very tightly and several folks have suggested some magic lubes on them (silicone based in one case). I think a light lube is probably a good idea, but why does it need to be anything special, and not "whatever good grease i have lying around?".
Any takers?
BTW, after what i presume is 27k miles mine are FILTHY! Disgusting!
With the caveat that I have no expertise, but can conjecture: Whatever you choose, it obviously should be minimally applied. Don't want it getting sucked in and be a dirt attractant in the intakes. Also, a fairly high melt point, and a minimum of volatile elements that could make their way into the intakes/combustion chambers, resolidify and "stick."