Black smoke out of my US Stove Corp pellet stove

[kylie]

Hi - I could use some help. Bought a US Stove 5500M pellet stove a couple of months ago. Installed it ourselves and it worked fine. Then, the problems started...First we had white smoke and half burned pellets filling up the firebox. Now the flame is all over the place and way too high, it made a "boom" sound with black smoke coming out of the chimney. Even had the fire dept show up! I have cleaned the stove countless times and just tried it again but the same thing happened. I called US Stove and they said it was probably the pellets, and that I should try to change those. We didn't pipe outside air in but are wondering if we need to. Also noticed that it looks like the rope gasket around the window doesn't fully go around, there's like a 3" space with no rope there. Is that normal? I bought it at TSC so it's not like I have an on-hand service dept to help me out. Just the people over the phone at US Stove. Any suggestions?