I have a 2 door Masterbuilt propane smoker. The first 4-5 times I used it it was great. The first problem I had was the flames/burner was giving off a heavy black soot or creosote that covered the meat and ruined it. I continued to struggle with the problem on 3-4 test runs. I completely cleaned the burner and that didn't work. I changed out the regulator and that didn't work either. The only thing that did work was to keep the burner as low as it will go and then the smoker struggles to get to 225. What am I doing wrong?