There is a thermo-vacuum valve at the front of the cylinder head. Should be red plastic! Only gets vacuum when the throttle is open. Allows vacuum to EGR valve above 50deg C & when the throttle plate is opened, venturi(or ported) vacuum.

__________________
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