A San Diego stock adviser who is accused of bribing an F.B.I. agent to give him confidential government information may have had prior knowledge of the Sept. 11 attacks, a federal prosecutor said yesterday. In a court hearing in San Diego, Kenneth Breen, an assistant United States attorney, said the adviser, Amr Ibrahim Elgindy, tried to sell $300,000 in stock on the afternoon of Sept. 10 and told his broker that the stock market would soon plunge. "Perhaps Mr. Elgindy had preknowledge of Sept. 11, and rather than report it he attempted to profit from it," Mr. Breen said. Mr....