Instead of using the DVOM, you can purchase a real Lambda tester for 300-400 dollars or so at Baum tools. Their site is Baumtools.com.
To pass the EMI, you will want to set it to 55% or so. I would think that the ignition timing would be OK> Since this is controlled by a computer (EZL controller), I have not seen the timing off on this engine.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS