I don't have an IQ, I do have a Guru which works flawlessly on my WSM's either bringing the temp up or down. When I tried to adapt it to my acorn it was an epic fail. first it wouldn't bring the temp up very fast, it turns out it was because of the air gap between bowl and cooker was just channeling the air around the lump and out the top vent instead of through the lump and stoking it. Then once I figured that out and decreased air flow it would over shoot not matter what I did with the top vent then as it attempted to bring the temp down the coals would go out by the time the temp dropped enough for the Guru to stoke again (this was while trying to see if the Acorn could hold 225 steady). I have given up (for now) and just control the temp manually.
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