Is there also a vacuum controlled flap in the intake manifold just before the EGR which opens and closes depending on the open/close of the EGR valve?

If you just block off the EGR, and the computer tells it to open and the intake flap to close a bit, and nothing comes in from the EGR because it is blocked off, won't the engine be "air starved" and not run right?

Isn't that why someone modded the EGR by capping the hole in the exhaust manifold and adding a small filter on to the EGR tube so that it draws in fresh air when the computer tells it to open?