Inconsistent running characteristics - a thought excercise.
 

My wagon finds itself mostly putzing around city roads and the driver is an energy conserving freak.

When it gets the chance to really advance the rack, the pedal goes for it. After this brief intermission form granny-driving, the engine runs 'healthier'... peppier... smoother.. higher idle RPM

...like someone just did a valve adjustment, or increased the fuel pressure.


This is not a 'messa a punto d'Italia' in the cleansing sense... it is not long enough in duration. 10-15 seconds max


any theories?

A bit of a quick injector nozzle clean!!??

Maybe the adrenalin rush puts the driver in a better state of mind, and all the world seems to have improved.

Does you engine have a ' rack dampner adjustment' available... and if it does... have you adjusted it ?
This was a feature the MB engineers designed into the system for a time in the distant future.. like NOW... when tolerances would need to be tightened up... due to normal wear...