SAS Arbitor 8 years old several 1000 rounds per year, multiple calibers. Once a year I plug up the exit hole, stand upright, fill with white vinegar, let set over night and pour out in the morning. Remove all fouling.
I have a SAS Arbuter Titanium. Have 1000,s of rounds thru it. Once a year I plug the end and fill it with vinegar, let set overnight, clean as a whistle.
No discoloration, no carbon.