Washington Mutual rode a huge $17.5 billion fourth quarter to claim its first-ever top ranking in the non-agency MBS market for 2002, according to a new ranking by Inside MBS & ABS. The Seattle-based mortgage banking firm ranked second in total non-agency MBS issuance in 2001, and saw its annual production climb 61 percent in 2002 to hit $49.2 billion. WaMu is primarily