I had the same problem last year and kept beating my head against a wall testing my EGR system which seemed to be functioning correctly. It turned out to be my 1 year old catalytic converter that had failed - with a new one it sailed right through emissions.

Testing is pretty simple actually, applying a vacuum to the EGR valve line while the engine is idling should make the idle rough. Applying 12v to the EGR solenoid will open it and allow air to pass through it - no air should pass without that voltage.

Testing your converter is as easy as shooting the inlet and outlet sides with a non-contact thermometer - if its working properly the outlet will be hotter than the inlet. Personally I'd test your converter first since it's the easiest and most likely culprit.

I'd volunteer my time this weekend but I've got until the end of the year to be out of my house and need to get packing and find somewhere to live.