Does a DI ignition module hold vacuum?

G'day Folks,


I'm chasing down what I think is a vacuum related problem on my W201 - M102.910 engine

As all vacuum comes from the intake manifold I've been testing from the two points where it originates (there are actually three but because I don't have an automatic transmission the third is blanked and is being ignored).

At the back of the intake manifold on the upper side there's a Y splitter that sucks to two places =>

1) the cabin blower motor controls (seems to be a some sort of semi-automatic blower motor system that has a vacuum switch to activate the flow of coolant through the heater matrix) and the adjustable headlights

2) the vacuum sensor on the ignition control module



The vacuum line is the only non numbered part on the module (#14) shown in this picture!

When I apply a vacuum to the line it doesn't hold.

I've only done this with the ignition off - I'm guessing there isn't any mechanical movement within that little box...

...so the question is =>

"Should this little bugger hold vacuum or not?"

I'm guessing it should.

I can't find anything in the FSM about this though (other than references to the vacuum line helping the module determine engine load)