Thank you for quick and valuable hits.

Yes, I've changed sensors on the right/passenger side. Two days ago had the same tought and almost had a panic attack.

I followed your advice and investigated fuel pressure regulator. All 3 (air pump valve, MAP sensor, pressure regulator) vacuum lines were changed and vaccum at low idle is .6 mBar=20 inHg. Regulator is closed when no vacuum. Found this generic info for other engines at http://www.mercedestechstore.com/pdfs/508%20Systems%20II/508%20HO%20Part%2007%20Fuel%20supply%20(WJB)%2004-01-01.pdf . Managed to measure rail pressure: 3.0 Bar at idle and 3.6 Bar for 4000RPM. So looks like regulator is OK.

Could you point me to good info on he web on how to check which injector might be leaking and how to test and fix them? By leaking you mean dripping/partially closed orfices?

Thank you.