staff review of the economics of bank mergers is causing turmoil at the Federal Reserve. The Fed is urging banks that serve overlapping markets to combine, in hopes of producing a more efficient financial system. But staff antitrust economists have found that cost savings from such mergers are realized slowly, if ever. A story about the internal review in American Banker, a trade newspaper, set off a search for leakers at the central bank. Although there has been no public word of any disciplinary action, a Federal Reserve official says: "Confessions were obtained."