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chib, with the huge caveat that I'm only speaking from my experience, so this is just fwiw. Btw, I have an EQ.
I have had a similar problem to yours, and I discovered there were two fundamental issues. One had to do with just finding the right usage technique for me, the other is a medical issue that is not that uncommon but still is little known to most people (as it was to myself).
The first issue is simply that I my respiratory system is just extra sensitive to heat and dryness. I combusted for years, without filtration or cooling, and rarely had an issue. But with the passage of time and relocating to a different climate, this sensitivity became more noticeable. This is common. When I started with the Q, I used passive direct draw @210c thru a 14" bong with a 6-slit stem; that required a lot of pull and didn't provide very good diffusion. Adding ice cubes seemed more of a hindrance than a help. I asked Kevin at Arizer what would be best for optimum density with minimum irritation, and he suggested dropping the temp to no higher than 190c and using the Fan assist set to 1 or 2. He was right. I also switched to the Headford piece that Nycdeisel has raved about, and she is spot on: It only holds a little over an oz, but the 11-slit inline chamber provides a lot of great diffusion; I've got a little tupperware bowl acting as an ice bucket for the glass which adds to the cooling. Then I fashioned a mini-bag that holds 5-6 hits, and use that thru the Headford rather than direct draw. Finally, I make sure my fill is right; with relatively good quality herb .15g is about right. This is enough for a very good high; if I want to go to the moon I use ~.25g and do the bag twice (Fan 1 actually results in more dense vapor). These changes greatly reduced the demand I was placing on my bronchial tubes in the draw, while providing a bit lighter vapor much more effectively moisturized and cooled. Does require a few more hits than a passive heavy hit at higher temp, so it's not quite as fast a trip but it's only a little additional time to get to the same place.
Now, after all that hoopla, here's the big surprise. Most everyone has heard of GERD or gastro reflux that causes heartburn, or inflammation where the esophagus meets the stomach. Well, there is a condition nicknamed "silent reflux", medical terms LRP (for "laryngopharyngeal reflux") or EERD (for "extraesophageal reflux"). These are called "silent" because in 50% of instances, there is no heartburn or stomach discomfort. The reason is that the stomach acid moves thru the esophagus more quickly and therefore concentrates higher up, primarily around the larynx. This causes radiating inflammation, for some a burning irritation anywhere from the upper trachea to the back of the throat. PPI medications often used for GERD such as Prevacid or Prilosec do not have the properties necessary to treat this type of reflux, which is why higher dosage Nexium is prescribed instead. This condition can only be confirmed by an ENT exam (which is no fun, but it's quick). I won't bore you with all the details of how I learned this, but I can say conclusively that this happens.
All any of us can do is share our particular experiences. I guess the lesson I learned is (1) try various adjustments in your vaping process, seemingly little things do matter; and (2) more can be involved than meets the eye, if a problem is outright painful and/or recurring something else could be at work and it pays to get it checked out.
Just my