Hi All, we've been working on our 1995 Corolla (1.6L, base model, auto-transmission) with a failed NOX emission test. Anyway, I have been learning a LOT about the EGR and related components. In our case the EGR wouldn't pull much of a vacuum until we got it off the car. We found the pencil / needle valve pretty coated with carbon. We also removed the EGR tube (it was the easiest way for us to get the EGR off the car with the tools we had). Anyway, we discovered the EGR tube was completely blocked (no light at could be seen from one end of the tube to the other). Had to use a metal coat hanger to clean out the tube of carbon. I don't know if this would cause our car to fail the Nitrous Oxide test at 15 MPH - but it passed at 25 mph but maybe people here might know if that matters. Also, I know there is a way to test the vacuum switching valve (with a vacuum and a 12 volt power source) but I am wondering if there is a way to test the vacuum modulator that is out of the car? I think I read somewhere that you plug 1 one of the 3 ports and then blow into one of the others and that you should feel the air coming out of the third port, but I am not sure. Anyway, they are only about $20 bucks so I can get one pretty easy, but I would like to know how to test it. I also want to say thanks to everyone here for all the help and advice already given - I DO appreciate it. Beyond that I want to say I hope everyone has a great Thanksgiving!!!