Check to see that the CIS system is recognizing electronic control. You can do this buy probing pin 3 of the x11 diag.port on the drivers side fender, or reading EHA current. At pin 3, you should see 69.9% duty cycle with the KOEO. At the EHA, you should see 20mA.

Without electronic control, there is no cold start enrichment and the engine will run crappy until warmed up. Hard to start as well.

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E