From your description it sounds like the dampener screw is too tight.
The screw runs horizontally into the back plate of the injction pump. Its head is 12mm wrench size and the jam screw is 14mm. If they look like they are made together (no threads shown) then you should replace the screw as the spring probably is too loose. Just backing it waaaaaay out will check to see if it is the reason for your sensitive cold idle.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician