For those who know what im talking about I would like to know if you ever needed to replace that fragile!high temp ceramic fiber in the back chamber.I have a new harman insert and wondering what the average life might be for this part?Heard its not a cheap part and hoping it would be covered under warrenty.I have been reading from others here on ways to keep that back chamber clean!The only cleaning i have done so far in its short usage is to place the vac hose up againts the holes to suck out what behind.When i get my stove liner and stove cleaned out from the harman dealers i bought it from!hopefully they can give me some good advice.I wonder how many owners know what kind of shape their back chamber is in.