Any suggestions as to why my vacum is at zero on idle, and only goes negative with a little throttle? It does go positive on boost as it should but means I have no effective DV.

I have removed the carbon can and replaced it with a 3 way joiner ensuring all one way valves in right place.

My icv is also vented to atmos, and breathers go into vented catch cans !

I'm guessing its something simple but stumped at the moment!

 

Must be a pipe off the manifold someware. take a good look around and i wouldnt drive as there is a good chance u have a lot of unmetered air going in. check all pipes on the manifold for leaks.

 

Been back through the pipes and only thing I can see is the icv ( the box to the left of the intake with the coolant pipes connected ) sucking in air through the breather filter- could hat be it as clearly under vacum?

Normally it's connected to the intake pipe

 

Use some brake cleaner or soapy water on all the vac pipes and especially all the pipes/connectors you have recently changed,im sure it will shows itself.