A subprime conduit that Washington Mutual launched late last year is off to a good start, officials say. The conduit is part of an expansion strategy designed to bring the lender more high-margin business while leveraging its existing capital market and loan servicing platforms. “We’re not new to this business,” said Doug Potolsky, a senior VP in charge of the WaMu program. In fact, WaMu has been buying subprime loans since 1999, with some