What is this blue plastic pancake vacuum can?

[Jetmugg]

I feel like I should know the answer to this, as I've been "into" these Benzes for quite a while. I have converted 2 1987 190D 2.5 Turbo's from automatics into 5-speeds, and on both of them, I have plugged the vacuum line that would normally go to the transmission.

This line originates at a blue plastic "pancake" style cylinder/can that is mounted on the firewall between the engine and the brake booster. I think it has 4 vacuum lines going to/coming from it.

I am having some other vacuum problems with my latest conversion, and I suspect that this blue cylinder is part of the problem. If this canister is only for the purpose of controlling the auto trans vacuum signal, I will completely bypass it. (The car has a manual trans now)

If it serves other purposes, then I'll do something else. Any help would be appreciated.

SteveM.