Just got my new set up of an Innokin Coolfire IV with ISub tank, it produces ample clouds and good flavor. Only thing that bugs me is a popping sound which happens on the first drag after it's been sitting idle for a while. Have set it to 23.5W with 0.46ohm and filled the tank with 6mg nic 50pg/50vg juice fm MBV. Is the popping sound normal and any suggestions on the settings would be appreciated!