I'm following this because both of the M103s in my sig just barely passed their most recent smog tests. Having 232,000 and 194,000 miles on them doesn't help any.

This is so out of left field but I have found that these CIS-E ECUs can kinda go south yet still seem kinda OK. I would never recommend anyone to just throw parts at a car but M103s are so plentiful out here in the U-Pull-Its these days that it's just too easy to get stuff cheaply and do a little experimenting. Any unused good parts are always good to keep as spares anyways. Most recently, I cured a high idle problem with an ECU change on the 89. Disbelieving, I put the original ECU back in for a week and the high idle problem immediately returned. Just remember to stay with 90 and later 3.0 M103 ECUs only as pre-90 ECUs aren't the same.
Regards, Eric

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89 300E "Benzer1" 15.924 Uncorrected
93 400E "Benzer3" 14.200 U.C.
95 E420 "Benzer4"
92 300E "Benzer5" 16.299 U.C. Future turbo CNG
87 300D "Benzer7"
87 300D "Benzer8"
87 300D "Benzer9"
87 300D/70 AMC Javelin "Sidewinder-Benzer"
87 300TD "Benzer11"
06 E320 CDI "Benzer12"
05 E320 CDI "Benzer12A"
71 AMC Javelin AMX 401 "Sidewinder"
74 AMC Hornet 401 "C.K.10" 13.63 U.C.
74 Bricklin SV1 "Presto" AMC 360 pwrd.