of course you have the updated wiring harness and checked the wiring on your Electronic throttle, right? These issues cause codes to trigger due to electrical faults and rough idle is always part of it, surging and missing. My 94 sedan had an upgraded harness but still had bad ETA wiring as indicated by the cruise control dropping out whenever I hit a bump, but otherwise it drove great..

Lots of comments about those issues here in the W124 threads. No need to repeat.