1999 Chevy Lumina code P0401 low EGR flow

Service engine light on. Code p0401 low egr flow. I tried a different valve from the junk yard (I cleaned the origional and the junk yard valves both with carb cleaner. They both seem to move freely). No change. The tube from exhaust is clear and has pressure, the vacuum from the intake seems strong enough and all the wires/lines/hoses appear good. After resetting the computer I'll drive about 1 mile and the light comes back on!
I'm in N.Y. State and this car will not pass inspect. With the light on. It's 11 days expired now and I'm getting desperate and frustrated! I dont have money to throw at random new parts 'till its fixed or pay a garage to do the same!
Help!