EGR systems consist of 3 main parts
1. EGR valve, it is attached to intake manifold and will have a metal tube attached to exhaust manifold
It is controlled(opened and closed) by the computer using engine vacuum.
2. EGR sensor, in your year this would be attached to EGR Valve, a PFE(pressure feedback) sensor, in later years it is separate piece, a DPFE(differential pressure feedback) sensor.
Yours has a metal rod that is pushed in and out as the EGR valve is opened and closed.
It also has a electrical connection that tells computer the rod's position, how far in or out.
3. EGR Modulator, this is a 12volt solenoid that allows computer to control the amount of vacuum it is applying to EGR Valve, computer pulses 12volts to this solenoid to open it a little or alot based on need and feedback from PFE sensor.
Best place to start is the vacuum hoses, a leak here will cause EGR valve to under respond to computer control..........signal is/was low
There is a vacuum hose from intake manifold to EGR Modulator, and a vacuum hose from EGR modulator to EGR Valve, check them to make sure they are air tight.
If you have a hard time finding it follow the EGR valves hose back to modulator.
Also remove the electrical connector on the EGR modulator, and make sure it is clean and dry, no corrosion.
While at the EGR valve check the electrical connector on the PFE sensor for same.
If hoses and connectors all check out OK then I would next test the EGR Valve by manually applying Vacuum to it.
Get a longer vacuum hose of correct size to fit on EGR valve, connect it to EGR valve.
Start engine
Feel the EGR's factory hose, put finger on the end of it, there should be no vacuum present on this hose, EGR system isn't used when engine is cold and isn't used until engine is under load, point of Exhaust gas recirculation(EGR) is to cool down cylinder to reduce NOx emissions.
If factory EGR valve hose has vacuum then EGR Modulator is leaking, replace it.
With engine idling suck on the end of the added hose, as EGR valve opens engine should start to stumble, and run rough, put tongue on the end of the hose and make sure EGR valve stays open, if engine starts to idle better EGR valve is closing so it can't hold a vacuum, it has a leak, replace EGR valve.
You can test EGR Modulator by applying 12volts and ground to it, there is no polarity, 12v on one pin and ground on the other will cause it to "click" open.
If you have a hose attached to either vacuum port on it you should be able the blow thru the hose when solenoid is open(powered) and not when it is closed(no power)
EGR sensor is harder to test, if above all checks out then I would replace it, about $25-$30
Welcome Visitor! Please take a few seconds and 
