I have a Fire Chief 700 wood furnace in the basement. Chimney is structural containing concrete block and tile ( about 7"X11") it is 33 feet tall with the top 20 feet exposed on all sides. Been burning for 35 plus years. Always had creosote/ drafting problems as the season progressed. Had a flexible stainless liner installed 11 years ago. It was not a easy installation and the liner had to be ovalized to get it down. Still having late season drafting and creosote problems. Thinking about having tile broken out and replacing with some kind of pipe. Recommendations?