On my W124 car, there is a switch over valve mounted on the firewall behind the brake master cylinder.
It has a black line (electrical) and a green line (vacum) connected to it.
The green line goes to the upshift delay valve on the side of the transmission.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".