Before spending money on the blockoff plates, run to a auto store (or a Harbor Freight if you have one there) and get a "brake bleeder & hand vac pump" kit. I got one for like 20-25 bucks and it has a gauge on it.
With this you can test the wastegates, egr valve and every other solenoid on the car.
It also gives you the capability to trace down leaks that you can't even hear. (My boost gauge was leaking pretty bad, but I couldnt even hear it at all,
)
Back to the EGR valve...the passages should remain sealed at rest. I believe it should start to open the needle around 1.2 in/Hg...I'll have to verify that. And also it should hold vac steady at about 16 in/Hg +