One thing that comes to my mind is your fire. What you see as being "smoke" isn't necessarily what puts the "smoke" flavor in the food, what you really want is that nice blue smoke that you hear mentioned. You may be starving your fire of so much oxygen trying to keep the temperature down low that your fire isn't burning clean enough to get that good blue smoke going. My advice would be to not fight the temperature, that gets old and is counterproductive. If the smoker wants to run 300, let it, every smoker has a little range where it loves to run, find that and let it run. There are a ton of people who prefer to cook at 300 and above.
XL Big Green Egg, Weber Performer Platinum, WSM 22.5"