For all of that smoke pouring out, air has to be coming in somewhere. The places where that happens is either the bottom vents or the joint between the base and middle section. The bottom vents close pretty well and I have run a bead of high temperature silicone around the bottom groove in the middle section.
It made it possible to control temperature. I also fiddled with the door to get the best fit possible. When I got my 22 I did the same thing. Since the tube of silicone was starting to harden, I used it up by doing the top edge as well. In spite of that, I get smoke leakage at the top edge and door.
Please note that this was immediately after I closed up the smoker and before I put any meat on. Usually I can get meat on within ten or fifteen minutes but for this smoke it took over half an hour before it settled down and I could put the meat on. I had no difficulty keeping temps between 225 and 250°F.