I agree that build quality declined after 93. Open deck blocks and plastic oil tubes attest to that (I also have a 95 E420 that isn't in my sig). I would even go farther and say don't get anything built after 2/93. As to M119 vs. M103 vs M104, all things considered, I would go with an early 93 320 or 400E. The 92 400E had a lower compression ratio and it's fuel economy wasn't as good. If fuel economy is really important, get the 320. I average 20 MPG with my 400E with a lead foot. I would average 22 MPG with a 320. You would probably do better in either. Every one of these cars has it's issues, check my sig, I speak from experience.

Please post what you get. If you get a 400E and you want to hop it up a little, let me know and I'll provide you a link to some good info.
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.