Hello. I have a Whitfield Pellet stove build before 1990. I believe it is an advantage II. I have not had any real problems with the stove over the years. This past winter, I purchased a pallet of ECOBURN pellets (made of ground up walnut shells, seeds, etc). This stuff is suppose to burn hotter and longer. I finally got to my first bag. After burning for 3 hours, I came home and noticed that the fuel tray was full of ash and burning pellets. The setting I left it on was #3 output. Prior to this bag of pellets, I have never had a problem with ash buildup using other brands of pellets made from sawdust. I"m thinking that the ash buildup has to do with the pellets being made of shells, seeds, etc (being dense and all). I have thought about upgrading my stove to one of those ultra-grates. But, since I haven't ever had a problem of ash buildup until I switched pellets, I"m thinking, why should I upgrade and most of all, will the upgrade solve the problem? I would not like to spend all that money upgrading it and the problem not being resolved Any help is appreciated. Thank you and happy holidays.