PokeyGizmo:
Is this normal with all adapters?
After discovering the adjustment slot (video) and playing with both (carto and the 510-901 adapter) I'm disappointed

I can't reproduce the vapor or taste that I get from the VKs batteries
Couple of things come to mind...
First, what is the voltage on your 510s? I am pretty sure that V4L batts rate a true 3.7v on a fresh charge with the newer XLs rating as high as 4.2v for a few, initial moments after charging. Lesser voltage could contribute to lower vapor amount and definitely different taste on juice. And aren't standard 510s rated at 3.2v? (I could be wrong here, but I think I've read that on the forums somewhere.)
Second, is your adapter making good contact with your PV? Sometimes the center post on a 510 will get "squashed" down by cartos and/or adapters and needs to be GENTLY lifted back into good position.
Third, do you have juice in your adapter or in your connection? It will dramatically decrease vapor and taste as it is impeding the current. I use pipe cleaners to clean the connection. I rinse the adapter in hot tap water and let it sit to dry for at least 90 minutes before replacing it on the PV.
Fourth, have you adjusted the airflow too loose? I have found that this can cause a loss of connectivity with the PV and the adapter. Try tightening it back down some and see if that helps (righty tighty, lefty loosy).
I personally haven't had any issues with the adapters I'm using from MadVapes. I use them on a 3.7 native 510 mod. I also have one adapter from AltSmoke, no problems either. In fact, I can't even tell them apart!
Hope something here helps, I'll watch for an update...