A faulty accumulator could account for all your symptoms except fuel consumption.
The only way the cold start would affect fuel consumption was if it leaked. If we were talking a US 380 then proper fuel consumption will likely occur with proper timing and closed loop fuel control. Read the archives about monitoring the duty cycle of the frequency valve at pin #3 of the diagnostic socket.
Proper monitoring of the duty-cycle can allow the proper mixture adjustment without exhaust gas readings.
Bosch Master, ASE Master, L1
33 years MB technician