Toyota Repair: EGR Problem, vacuum source, vacuum hose

Question
Sir, I have a 1990 Camry V-6. 151,000 miles. I have a check engine light and I did a diognostic and received a code 71, EGR system problem. Gas mileage went from 24 MPG to about 16 MPG and it seems to have happened abruptly. I get a lot of white exhaust that smells like it has a lot of unburnt fuel. Idle is erratic at times. I changed the EGR Temperature Sensor as well as the EGR modulator. Still same problem. Now I am thinking about looking into the EGR Valve. It looks kind of difficult thought. Any idea of where I can go from here or maybe I should go back and double check something? Thanks for your help.
-Thiseas M.

Answer
You can check the egr valve before you replace it, it may be leaking internally.
With the engine idling normally remove the single vacuum hose that connects to the EGR valve, on the manifold find a direct vacuum port and connect a hose directly from the vacuum source to the egr valve,if the valve works it should either kill the engine or cause a very rough idle, if this happens remove the vacuum source and the plug the hose, the engine should run normal, if the engine still runs rough the valve is sticking open and needs to be replaced, if the valve passes this test let me know and I have some more info for you.