I'm using efest batteries in my kts mechanical mod and an igo l rba. My airhole is right on top of the coil and I'm using 50 50 blends...also even when I clean it out and build a new coil it still tastes a bit like the last juice I was dripping with it. And I check for hot spots and don't see any... It's fine on my vamo but not on my mech.
The IGO-L is a nice little RDA. I have three...love 'em.
Some flavors tend to linger and don't disappear right away even with a good cleansing so I wouldn't worry about that (I tried a buddy's RY4 with one of my SS drip tips and it was two days before I stopped tasting it...even after cleaning the heck out of it...which is why I have three IGO-Ls).
Odd that you don't cough using the Vamo. I would think it would be the other way around due to the Vamo's pulse modulation.
Dang...It still sounds like you've got a hotspot somewhere. Any chance it's on the bottom of the coil or on one of the legs maybe hidden by a screw? The legs are the usual suspects...they need to be the same length or one just gets too hot.
What ohm is your coil and what voltage are you vaping at on the Vamo? Could be your mechanical is a bit too much for it at it's current voltage level.