Hmmm...I have the same idle fluctuation problem...but mine acts up in D or R (especially R)...more prevalent in warm weather than cold.
Swapped out the air flow unit with a new one, and the problem persisted, so I returned the new one.
Was I wrong for doing this?
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car