five-oh,
Without diagnosing your problem, I will say that when I was the cleanup flunky in my cousins repair shop in the dark ages, we would take nasty old fouled draft tubes off and throw them in a burn barrel.
When they came out, they were squeaky clean inside and out! Burn barrels are outlawed in my neck of the woods now, and this might have been a environmental disaster, but it sure got the draft tube clean. Good luck!
Stuart
