skiddusmarkus

I just fitted a breather system following the instructions from theGTIROC.I used the old pipe that went
from the t-piece(on the right hand side of cam cover)to the induction
pipe to connect the top hotizontal pipe of the new breather to the t-
piece.I connected the diagonal pipe on the top of the breather to the
induction pipe with samco.I connected the horizontal pipe at the
bottom of the breather to the sump return.
When I run the engine,I can feel that the vertical pipe at the bottom
of the breather(thicker than the others,not connected to anything)is
sucking ie there's vacuum.This is causing the car to idle worse(it
doesn't idle particularly well anyway)than before.
Have I done something wrong somewhere?Should this bottom pipe be
connected to anything?Someone has suggested blocking it off and when I put my hand over it,it does idle better but why is it on in the first place if it causes problems?
Secondly,as I've removed the old breather I can see that bits of the
manifold gasket are flaking off,could this be a cause of bad idling?