Burnt taste generally indicates to high a wattage, I use temp mode with SS coils in the RBA deck and am still using the original coils that came with the deck. 350F temp with 35 W preheat and this is dual coil TFV8. I've run into times when I accidently held down the fire and after could taste a little burning, I went down on the wattage and preheat and continued vaping, after a little while the burnt taste was gone. Sounds like you are doing well with the 12, I do think it is a good tank although not used much I'm glad I bought it and tried it.