Originally posted by M.B.DOC
California required fuel system fault self diagnosis in their emission program. THAT is the major difference. Also the M103 engine needed an EGR valve for that emission program. The federal version didn't get an EGR valve until 1990 & the self diagnosis was never as good as the Calif version.
I worked on an awful lot of M103's under warranty here in California, personally I do not recall them having EGR valves fitted on them until 1990. Without going into any details about electronic control differences I do recall the fuel system for Cal being fitted with fault diagnosis and a "Check Engine" mil. To my knowledge this was/is the single most difference between Federal and California vehicles of that era.