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You've got it backward. The Lean Burn computer on the 1978 Omni I once owned provided spark control only - no fuel control. The computer on my 1985 Diplomat provides both spark and fuel control. In fact, the computer is marked "Electronic Fuel Control System" (see picture). The 1985 engine is equipped with an oxygen sensor and a "O2 feedback solenoid" in the carburetor for fuel control. According to my 1988 service manual, this setup was used in 1988 as well.



Electronic feedback carbs and lean burn are not the same thing. Lean Burn cars did not use the O2 feedback. Lean Burn cars had a throttle sensor on the carb and the carbs were are smogged out as you could get with terrible jetting, and idle/transition circuits. They were setup to run with the advance curve built into the lean burn computer, nothing else. You're right, the later ones had the electronic feedback carbs and the o2 sensor and they were a lot better than the Lean Burn cars. The computer adjustability and o2 sensor to keep things in check was much better in terms of driveability than the Lean Burn cars, which are the one that earned the system the bad rep. The feedback carbs are perfectly driveable when everything is in good shape and functioning properly. I think with the 80's ESC cars, you can swap off the feedback carb and retain the computer spark control with the 80's computers delivering a better spark curve by those years. Trying that with a lean burn computer and you get a real dog. IMO at the end of the day your best bet is to replace everything or keep everything.

You are correct in that in those years the 4cyl cars were available with electronic spark control with or without electronic carbs or lean burn carbs, but you can't really compare them to the V8's of the day which had entirely different equipment.