I am looking into a lot of variables, but so far it's looking like the biggest factor is the simplest; having them filled with PRECISELY 1ml. Not .9, not 1.1, but 1.0 exactly. I did a LOT of testing and that is the sweet spot.
That's something Steve's been trying to get them to do for a LONG time, but they kept insisting that that was too much. SO before I left, I made a video for them showing me filling a blank cart with 1ml, and comparing its vapor production to one of their .8ml prefilled carts. My 1ml cart blew their .8ml away.
Now, they're finally doing 1ml. And most of the carts I've tested have all produced GREAT vapor. They fill by hand, though, so there's still some inconsistency. I now have them checking the fill by weight, though, so we'll be getting even that smoothed out.
The remaining problem is the tendency for some flavors to need several puffs before producing their maximum potential vapor. That one is going to be a bit harder to nail down, because it varies by flavor, so it's not the carts themselves or the fill amount or method but believe me, I'm working on it.