Don, I just figured that if pulling and cleaning the plugs would take care of carbon build up they would not have a tool to go in there and ream...It was just an "old mechanic" guess that led me to that place... I have no direct information about the carbon placement... but plan on pulling my precombustion chambers the first chance I get....
If what you did could normally be expected to make an improvement and did not, then I would think going back in and reaming would be logical....
If you do ream I suggest that you pull the injectors and vacuum from the top with the glowplug holes open before buttoning back up....