The 1990 California emissions cars use the same system as later LH fuel system cars(for monitoring). The air injection & EGR is monitored thru the O2 sensor & the ignition system(map sensor in EZL). Could be as simple as broken vacuum line from electro-switchover valve to diverter valve. Many Calif cars had a recall on the EGR code 16.
[This message has been edited by M.B.DOC (edited 11-23-2000).]