Here's a secret "they" don't want you to know about testing the mechanical part of the EGR system. (if all is working, remember, the computer is what tells the valve "when" to come on, BUT, the computer is RARELY the problem with EGR troubles).
1. Locate it on the engine (Bigpetes is on the rear end of the exhaust manifold)
2. disconnect the vacuum line on it
3. attach one of your own (bought at a parts store for pennies, 3ft)
4. with your mouth, suck on vacuum line firmly. A good valve's diaphram will hold vacuum. If air keeps coming in, (like a straw) then the valve is bad. = replace valve
5. if valve seems good, start engine and let idle. Apply vacuum again. Engine RPM should drop because you are allowing exhaust gas into the fuel mixture at the wrong time.
This system is working properly. Do it several times to learn how it effects idle, and to feel good that you did it yourself.
6. if engine RPM does not drop , then the tubing and/or ports are likely plugged with gunky egr goo, and won't allow flow.
That may be a job you can do, or not. But you yourself have now tested the mechanical portion of the system.