PIMCO: End of mortgage buys form of tightening Jennifer Ablan Tue, Mar 16 2010 NEW YORK (Reuters) - The end of the Federal Reserve's program of purchasing $1.25 trillion of mortgage-backed securities at the end of March is a form of tightening monetary policy, the chief of the largest U.S. bond fund manager said on Tuesday. Mohamed El-Erian, chief executive and co-chief investment officer of Pacific Investment Management Co, or PIMCO, said the end of the Fed's mortgage program, one of the U.S. central bank's major support programs, signals a form of credit tightening. The Federal Reserve Open Market Committee's...