I notice the draw is a lot harder when the carto is heavily saturated with juice. I get the best draw and vapor by limiting the amount of juice in the carto and replenishing it more often. I also get better control over how much juice it put into the carto by refiling it through the battery end with a syringe, instead of using the condom method.
DocWyatt, have you looked into using a larger battery with a 4081 adapter?
That's because using the condom method saturates the filler way too much,
not allowing air to flow through the filler, which causes harder draws. Then you have the mess to clean up and excess juice to blow out.
I don't know what kind of cartos you're using, but if you have the Boge 510, SLB 510, 4081 or KR808D-1 cartos, it's much easier to just drip directly into the filler from the mouth end. Then you have no mess to clean up (no condom, syringe, needle, and desktop to clean) and you've saved time, because it's so much quicker to refill a carto by dripping in about 10 to 15 drops directly into the filler (depending on how empty the carto is).