The Second Air (gsf1200w/x E18) assembly is constructed from several parts from which the Valve Assy,2nd Air Reed is the most expensive.
The twenty-six Gsf1200s 1997 (v) (e02 E04 E17 E18 E22 E24 E25 E34) Second Air (gsf1200w/x E18) component parts are all listed in this schematic.