Perhaps I'm a little confused here. A little clarification is needed to help me understand the full scope of the problem. The EGR opens and provides a common path for the gasses to be re-circulated, hence the name. Those two "slots" are plenums that you're viewing are likely one going to the common intake manifold and one siphoning off spent gasses from the exaust.
So when you speak of the slots sucking air are:
a. You watching the action with the EGR valve off the maifold?
b. You watching the action with the EGR mounted to the manifold?
If the common intake manifold plenum is sucking air and dumping vacuum at idle when the EGR is installed then the leak has got to be fixed. The problem would lay in only one of two places:
a. The EGR valve is bad, it's stuck open a little bit or not able to close.
b. IF the EGR gasket is compromised it can also let air transfer between the two pleneums.
Is it possible the EGR-TVS is installed backwards?
In either case, at idle, the common manifold vacuum should not be dumped by any part of the EGR assembly, pintle or gasket. It's got to remain intact or rough idle will be the result as the vacuum sucks air and leans out the mixture.