Please bear with me there will be alot of pics.......So I can't clean my pipe the way most people do with torches or fire pits or so forth because it is a Tecnigas Next R chrome exhaust so I had to figure something else out for it. My fix was a industrial strength Drano which was almost all Lye and a toilet auger. First I put the drano in and this stuff heats and foams up good this got a ton of gunk and carbon out. Then I shoved the auger down both ends and twisted and pulled and this and that. Then once more with Drano the lye eats through oil and anything like it ain't nothing finished with a nice polish