Fuel mixture / air mass sensor can cause this type of problem, and can be hard to find. If there was any electronic accelerator/ idle speed control problem there should be a CODE in the ISC/CC computer. If air mass sensor is the problem the shop should be able to go into actual values in the HFM(fuel system) computer & read the adaptation values to see if the system is running LEAN.
Good Luck

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator