Vacuum leaks as suggested in your other post replys will make car idle too high, not run rough. Are the plugs showing burning too lean? You mention not fouled. If so after checked from drive, should check Control & System Pressure in FI System. Could still be a electrical weakness with ignition system, even thou replaced main parts

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83 280TE- 5 spd, 16.5mm rear sway
85 280SL- 15" Bundts, 5 spd