How to test Toyota EGR System(VSV, Vacuum Modulator, EGR valve)

How to test the components of a Toyota EGR system, including the EGR valve, VSV(vacuum switcing valve), vacuum modulator, and throttle body. Toyota EGR specs and testing: http://motor.com/article.asp?article_... http://motor.com/article.asp?article_... http://motor.com/article.asp?article_... http://motor.com/article.asp?article_... Schrodinger's Box Diag+Understand EGR System:    • EGR P0400, P0401- P0409 Diagnosis+Understa...