1997 Toyota Avalon, 183K... Check engine light came on--code shows EGR trouble. I checked the EGR valve per the Haynes manual--run engine, disconnect vacuum line to EGR, attach manual vacuum line, apply vacuum: if the vacuum is steady and the car runs poorly then EGR is ok. That is what happened. I would like to check the vacuum switching valve to see if vacuum is getting to the EGR valve--since there is not supposed to be vacuum at idle, how can I do this??