The FBI's 1,600 page informant files on Winter Hill boss James "Whitey" Bulger and his one-time enforcer Stephen "the Rifleman" Flemmi reveal that Flemmi "provided more intelligence on the New England mob than Bulger" as reported by Tim White for WPRI: "the files show Bulger was an informant from 1975 to 1990 while Flemmi's years date back to approximately 1967," and "Flemmi's access to members of the Patriarca crime family was evident in several references."
Of couse, as an Italian Flemmi obviously would have had "far better access" to the wise guys as aptly noted by Boston Globe investigative reporter Shelley Murphy who has co-authored a book on Bulger:
"Flemmi, the son of Italian immigrants, had been offered membership in the Mafia," Murphy said. "[Flemmi] politely declined because he didn't really like them that much and it was more lucrative for him to work with Whitey with the protection of the FBI."
The murder trial against Bulger is set for this June, and among the government's witnesses will be Flemmi. There's "no love lost between these two," and "Flemmi claims he thought about killing Whitey" as reported by Howie Carr for the Boston Herald.