Complex sentence: The original Critters Buggin trio continued with several guest musicians, including Mike Dillon, who by 1998 had joined as a fourth member, thus forming the current line-up as of the 2004-2005 release and tour of "Stampede".
Split into simpler sentences: The original Critters Buggin trio continued with several guest musicians, including Mike Dillon. By 1998 Dillon had joined Critters Buggin as a fourth member, thus forming the current line-up as of the 2004 release of "Stampede".