Dumped out the old fuel, outside the tank it was slightly cloudy and going amber. Rinsed out the tank with fresh fuel until black bits stopped coming out; I fear the wick may not be in the best shape. A good old fashioned soap and water scrubbing, and then put the large pot on to boil. It would get right to the brink of boiling, but ultimately was unable to do so without the lid on, nor would it maintain a boil without the lid. Putting the lid on for about 30 seconds got it there, though. Afterwards: No soot on the pot. I've yet to change the SRV pip or cap gasket, there might be some performance gained there. What say ye folks, is this how a 123 is supposed to behave or is there more there? Thanks everyone, I very truly appreciate the help and advice.