Toyota Repair: High NO2 level, vacuum hoses, vacuum diagram

Question
My 94 4runner V6 has a very high NO2 level. All other byproducts are good to go for calif smog.
I hooked a vacume line to the EGR valve. The engine  stumbled for a moment them resumed its normal idle. No additional stumble.
After the car was well run, I checked the vacuumed line to the ER valve at KS rpm. No vacuumed was detectable.
How do I trace the vacuumed lines. Is there a clear diagram that show the location of the switch logic?
Should I replace the ER valve?

Answer
Unless the check engine light is on the EGR system is probably function ing correctly, has the ignition timing been checked, it should be at 8 degrees BTDC, too far advanced timing can cause high nox readings as well as the engine running hotter than normal.
The EGR modulator valve which is attached to the EGR valve can cause a problem so try replacing it. Check the vacuum hoses that connect from the modulator to the throttle body, check the vacuum diagram under the hood and make sure none of the vacuum lines from the valve to the throttle body are mixed up.