An easy test for an operating EGR system with the
vac. pump is to pull vac on egr when car is at idle.
The valve should open and make the idle very rough. Release the vac and it shoud even out.
However, It should be noted that some engine are prone to a blockage at the intake pipe from the egr valve. This will
diagnose as a bad [ non-opening] egr. [104 engine is a common case in point. [see SB's article in DIYer section]
That can be diagnosed by opening line at egr [ pipe running from egr to intake], and feeling for vac with thumb at idle, No vac= plugged pipe.