2001 Honda Odyssey EGR VALVE

Sorry, this is not a direct answer to your vacuum check question.
FYI. Honda has extended the warranty against the ERG valve clogging or becoming contaminated to eight years or 80,000 miles. If your van suffers from these ERG valve problems and qualifies for the extension, a Honda dealership should repair the problem free of charge. I hope this is of interest to you.