I bought the same one the first week of January. When I seasoned it, the chips started on fire. I thought I must have had the burner on too high and, like you said, the thermometer barely moved. A few weeks later, I stuck a butt roast in there with a cheap surface thermometer which showed I never was able to get it above 220, even with the thing running full force. The roast took about 10 hours to get to 190, which I guess that's not that bad. Yesterday, I did a whole chicken and couldn't get the temp over 205. The wood chips started on fire that time too. I should add the temp here in Iowa was around 45, and it was windy all three times. I haven't done any mods yet even though I have the gasket in a bag by the back door. I ended up finishing the chicken in the oven (I guess the wife and son wanted to eat before dark), but my 5-year-old ate more chicken than I have ever seen him eat before in his life. He even asked for it for breakfast the next day (he usually says he doesn't want breakfast).
I think next time I am going to try to move the chips up the top of the rails in the lower position or even to where the water pan is and move the water pan up to the lowest position in the top section. I also wonder how much the outside temp makes a difference, and will know that in a few months.