The Federal Reserve Board’s new final rule on high-cost mortgages could induce subprime mortgage lenders to cast more of their new loan production as second-lien loans. In a long-awaited final rule approved this week, the Fed cut the interest-rate trigger that defines a mortgage as high-cost under the Home Ownership and Equity Protection Act to 8 percent above comparable Treasury securities. But in a shift from the agency’s proposed rule issued a year ago, the