I suspect most of the leaks were coming from the NY field office...they hated Hillary. I also suspect they were advising Comey about Weiner's emails and leaked directly to Guilliani about Comey's October Surprise announcement....
"....F.B.I. agents still tend to be white males. In a way, this situation is systemic: to be promoted, you have to be willing to relocate, which can be difficult for women with children. A current agent also says that there’s a strong conservative bent: if a TV is on in an F.B.I. building, it’s likely to be Fox News.
But even within the F.B.I., there are tensions. “There are three F.B.I.’s,” this agent tells me. “There are the [56] field offices, there’s [headquarters in] Washington, and then there’s [the field office in] New York.”
Often, a retired agent says, those in the field are suspicious of Washington. “Dreamland,” they called it in his day, because they believed those who weren’t on the ground investigating cases were clueless. “[Agents] out in the field never want to give a case to D.C., because they believe headquarters is a hindrance to their investigations,” says the agent, who also notes there is a paranoia that politics might interfere at headquarters. New York has an especially dim view of Washington and a reputation for fierce independence. “
There is a renegade quality to the New York F.B.I.,” says a former prosecutor, which, he claims, can take the form of
agents leaking to the press to advance their own interests or to influence an investigation. “
New York leaks like a sieve,” concurs another former prosecutor..."
Comey made the decision to run the investigation out of D.C., not New York, despite the fact that Clinton and her server were in New York. A core group of investigators and analysts were vetted and given security clearance, meaning that only those who were working on the case knew what they were doing.
Comey chose Washington because he wanted to be close enough to get daily updates, according to CNN, but
he may also have been worried about leaks from New York. A former D.O.J. official says that, as early as 2015, a rumor was floating around that
the F.B.I. agents in New York were cracking jokes about seeing Hillary Clinton in handcuffs. “It was widely understood that there was a faction in that office that couldn’t stand her and was out to get her,” this person says...."
https://www.vanityfair.com/news/2017/02/james-comey-fbi-director-letter
Too bad the agents didn't say it in an email.
