Technical EGR question

[Mrkentee]

In a stock engine, when the egr valve opens, is it more exhaust pressure pushing the exhaust gas into the intake manifold? Or is it the venturi pipe causing it to be sucked in.

Another way of asking: when the egr valve is closed, how much pressure is in the egr cooler waiting for the valve to open?

[Lonestar10]

Typically exhaust pressure is always higher than intake pressure when under power. Not exact but figure 2 lb on exhaust is around 1 lb on the intake