This is my third year running a King Ultra up till now no probs got through last week -47 wind chills just fine. Now in the last two days the King started drafting poorly despite whatever setting it was put on ,the coal bed started building up and wood was burning sluggishly.Also we could smell smoke in the house something that has never happened,heat output was poor.This fall I had a four foot extension put on my chimney,I found out that the clown who put it on used rigid chimney liner,and up till now the thing worked as a King should,I'm guessing that the extension has creosoted up ,thus restricting airflow and draft do any of you believe this is my problem,I plan on going up on the roof today to try and resove this problem as a huge arctic blast is headed our way tomorrow,Thanks in advance.