In general, EGR valve needs to be connected to a ported vacuum source, (Located above the throttle blade) not manifold vacuum, it should never come on at idle. Usually, there is a thermal controlled vacuum switch to prevent it from coming on when the engine is cold, sometimes a computer controlled switch is present to limit it's function, too.
The test you performed with the valve actuating enough to stall the engine, and the fact that it holds vacuum shows that the valve is working, and the passages in the manifolds are not plugged with carbon.
Do you have it connected to ported vacuum on the Weber carb, or did you have it disconnected because it was stalling the engine?
Do you have the readings from the test? Does a VA smog Test give 5 gas readouts? There is a free online "Lambda" calculator that can tell if your engine is running an air/fuel ratio that allows a cat-converter to properly catalyse the exhaust.
http://www.smogsite.com/calculators.htmlScroll down to the "Lambda Calculator, input your readings and calculate the results. If the mixtures are correct, the EGR is working properly, the timing is set correctly,and your readings are still too high, suspect a Cat Converter.
Another clue to if a high NOX reading is a result of a bad Cat-Con is that there is also a fairly high, yet still passing level of CO reading, as a properly working cat-con is using the CO to convert the NOX back into Nitrogen by stripping the O from it and converting the CO into CO2.
ANY exhaust leaks above the cat-converter need to be repaired. An example would be a gasket that's blown, or a cracked manifold or head pipe. Air getting into the exhaust stream can ignite the CO before the Cat-Con can use it to convert the NOX.
