We bought this multifuel stove in 2009. It's a bigger one, supposed to heat 2200 sq ft. We just recently started having problems. My buddy bought some Michigan wood pellets and he said his stove didn't like them. He wanted to know if I wanted them, I said sure because between last year and this year I've burnt 4 ton of those without any problems. I got them and after a couple of days started having issues with dirty burn. Glass would turn black, burn pot would overfill in 6 hours on the lowest setting, faster the higher the setting. So, I thought junk pellets. I've now tried 3 different brands with the same issues. One might burn a little better than another, but end up with the same issue. I've contacted Englander 3 times and with me guessing and them telling me what to do this is what I've done; 1)replaced hopper, window ,door, and ash pan gaskets.2)Replaced the exhaust blower.3) cleaned it really well twice by taking everything out of the firebox, taking the little doors off that allow you to clean out the heat exchanger, hit behind the fiber board with a rubber hammer, shoved a piece of wire down each hole in the heat exchanger to make sure it was clear. cleaned everything I could reach when the blower was off.3) cleaned the exhaust pipe.checked for blockage on the intake side which has an outside air kit.5) they had me check all the factory settings after a factory reset of the unit. Had me make sure the low fuel feed was set on 1, it was. check the low burn air was on 6, it wasn't it was on 4 put on 6. Air on temp was on 1, it was. also checked to make sure it was set to pellets which it was before the reset, and after it was on 3, which is strange because that's not a factory setting for anything.5 is corn. 4 is cherry pits and 1 is pellets which I set it at.6) the burn pot and stirrer were new this fall. Right now I'm tearing it apart again. They are convinced there is a restriction somewhere in the air flow. I'm quite sure there's not, but I'm checking. I'm starting to think maybe a circuit board? When this first starts up all looks good for an hour or two, then starts to go down hill. I also noticed there are 4 small holes in the heat exchanger behind the fiber board, odd shaped and a little smaller than a pencil. Look like welds that burnt through from the other side or made the metal thin and slowly appeared. Think I might put some jb weld in those. Englander didn't seem concerned with those. Any help is appreciated. I'm cleaning it real good again, then I'm heading out to find some different pellets again, I need more anyway to finish the winter. Thanks for reading this long rant.