Here's something different. A friend just told me that when dripping they pulse the battery while they are taking a hit. It causes the juice to to stay much cooler and equals a cooler vape, plus it won't burn the juice. The longer the push of the button the hotter the vape will be.
I use an Igo-W also. My friend can not vape on it. Even with 2 air-holes and 30/70VG. I don't mean to sound like there isn't a way around it but she does not like my set up, and I don't have a for sure answer on how to fix that for her, either.
There's so many variables. I had one flavor that absolutely killed my throat! An evening of vaping and I would wake up in the middle of the night due to the pain in my throat. All from one lousy flavor that I happened to adore. Lol!
Check to see there is air space underneath each of the coils and not just cotton there. Air needs to pass below and above the coils. if not this will also cause cotton to burn, and or give really *harsh* hit. (I apologize if I'm being redundant and you already know all this)
Also, you won't know the cotton is burned until you pull the cotton out from inside of the coil. You don't even have to unwrap to find out. Just pull it a little bit one way or the other to see.
Long shot, but, if a coil has gunk built up on it, it too will give a harsh vape. I know it's a long shot since it sounds like you haven't used this coil for long but hey, it might help someone else, too.
Now I'm really curious as to what the solution is for this. Sounds like a lot of trial and error. Great suggestions here. I'm learning a lot, too.