There is no conceivable way the kabuki itself will change over time with normal use. Temperature is nowhere near hot enough to change the metal. So here are some thoughts as to why you might be experiencing this.
I am thinking it must be gumming up from your juices. I seldom clean my stealth bukis because the coating is so fragile and I don't have the problem.
Having said that I do notice a difference when I go from one of my RBAs to the kabuki.
I seldom use thick juices in this tank as the coils to gunk up pretty quickly.
I would definitely try the ultrasonic cleaner - this will bring it back to - as new
Thanks
No, I wasnt implying that I thought the kabuki itself had changed, i was wondering mainly if the aiflow part could be that gunked up inside...and that probably is the reason .I do use heavy VG juices, at least 50/50 lowest %, AND they tend to be sweet fruit &dessert flavors...so yeah,ill try the Ultrasound