EGR Block off neccessary w/boost?

When boost is applied to the intake manifold, does potential intake air escape through the aluminum hose that goes from the manifold to the header? I was thinking about this and figured it would be a good idea to block off the 3 EGR ports all at once. Let me know what you guys think.

Thanks,
JR

That's not a problem, but most people do it to keep that heat from going into the engine.

Is there any mechanism in place which restricts the flow to one-way only?

I think they have 1 way valves, but the EGR will open only under certain circumstances, and WOT when you're making boost isn't one of them.