You can try and vape just the PG and then the VG seperatly with no flavoring added and see if either one of those are giving you the problem. If not then mix some NIC into the VG and see if that's the problem. If those are not the problem then it could be your flavoring or vaping hardware. If both the VG and PG vaped seperatly are giving you the same harshness then it could be your hardware (Burnt coil, to high a voltage, burnt or caked coil and wick).