That is your vacuum distributor block
P intake manifold vacuum (grey)
1 PSE control module (transparent)
2 A\C system (medium green)
3 A\C system vacuum reservoir (red\grey)
4 Upshift delay vacuum actuator (black\grey)
5 Automatic transmission vacuum reservoir (black\grey)
Check the vacuum distributor block sometime it leaks.
part number for vacuum block is 129-800-14-78
also it has vacuum reservoir inside your right front fander if the reservoir drops below 400mbar the PSE pump will starts until vacuum of approx 600mbar is obtained.
MB STARS Master Guild Technician,17 years MB tech
14 years independent shop owner