After replacing the wiring harness, I think your next step ought to be to check codes out of the DM to determine what is causing codes to pop up.

You might also need a throttle actuator, mass air meter, or might even have a simple vacum leak somewhere causing the idle fluctuation.

An injector problem would be the exception, not the rule.

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".