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I completely agree with @Tjcoley if you are simply looking for a cooler to FTC. Those thick cheap (or free) styrofoam coolers are more than up for the task. I have held a 9lb butt for 7 hours and lost only 10 degrees.
How long after you lit the lump did you wait to put the meat on? Was it fresh lump? If it was fresh and you were quick to cook, perhaps you are tasting VOCs. Let the Egg stabilize for about 20 minutes at your desired temperature. The exhaust should be nearly odorless at that point. Perhaps that will help.