I have a Jotul 3 Classic gas (NG) B vent stove. It's about 10 years old. During the last season it started burning very rich and sooty with crud building up below in the burn chamber. I'd clean it out, run it another month, and end up with more soot and crud. When I say crud, it was piled up right to the burn tube sometimes. So I first opened the air intake near the base of the burn tube to see if this would balance it. I then realized the burn tube itself was completely corroded and cracked, and with a lot of trouble from Jotul replaced it (it is the one piece "U" type tube and it cost almost $200). All this history brings me to the problem and the question.... Now the stove lights but doesn't stay on. Furthermore, without any change to the gas pressure (which is normal) the stove is totally over fired when on with huge flames. Nothing has been touched on the stove valves and the new tube is OEM perfect. I have trimmed the gas pressure with the house gas line's valve so the flames are normal height, but the stove still kicks off after a few minutes. What is going on and did something happen when it was sooting heavily to burn out the stove's gas valve? I should mention that I have cleaned thermopile, thermocouple, and bypassed the spill switch (just to check it) and they all seem fine. Thanks for any help.