Were these Tobeco KF4s purchased from same supplier at same time? Tobeco has only recently (in my experience) stepped up the quality of products. They used to be so-so. It is entirely possible to get two bad units, after all these are just cheap clones. That said I find it a bit unlikely to receive two from different batches with same issues.
Not saying it IS user error, but it does come to mind. What have you done to these when they arrived? Leaking from where? Sorry haven't read your other posts if you've already mentioned. I'm no pro here, but in my opinion leaks on this device can be caused by two things, loss of pressure, or poor wicking, leading to flooding. You've already got the orings on the way so hopefully that will cure your leaking.
As for AFC it is a quite simple arrangement, if it isn't doing its job its simply not blocking the holes. Why isn't it blocking the airflow path? Only a very limited number of possibilities, either threads were not cut deep enough to allow the grub screw to turn in far enough, or it is completely undersized, doubting the latter.
One of my clones (not Tobeco) the grub screw would not turn in far enough to do anything, burrs left over during the tapping process caused this, simple fix, work the screw in and out. Take a piece of wire or something small enough to fit in the center post, use it as a measure to see if the grub screw is going in enough to block the air path.
As for people "raving" about individual experiences with the Tobeco, would you rather we not post anything? All any of us can do is convey our experiences with products we acquire. As I've already mentioned, I've purchased 3 different clones from 3 different manufacturers, fit, and finish on all three are pretty good, I've got to look extremely close to tell much difference. Function was another matter, one of the three, that being the Tobeco did not need work out of the box.
Sorry but your usage of the word "raving" seems a bit out of context, I've not seen any posts I would consider raving. Overall the failure rate of the Tobeco seems very low, is it the best choice? Maybe not, is it perfect, maybe not, but I've seen much less negative commentary on the Tobeco then the other commonly purchased clones.
Overall the KF4 would not be my first recommendation for the inexperienced, it is not as forgiving as many rebuildables. Honestly if your looking for a perfect KF4 experience perhaps you should just buy an authentic? As for clones, I'd bet the Infinite, or SXK will end up being top notch copy, based upon my previous experience.
