Quickest way I have found is to grab a vac line that is functioning at idle and plugging it into the top. The vac lines that come off the plenum right next to the EGR valve are good examples. Just unhook from your favorite VSV and connect to the top of the EGR. All this will prove is if the EGR is opening when vaccum is applied. If the EGR isnt shutting and sealing then the only way to check for that is to block off the flow into the plenum or remove the valve and try blowing air through it. Without vac. applied air shouldnt be able to pass.
Another favorite tool of mine is them light bulb shaped rubber baby snot rags? Works great for pulling vaccum amoung other things.
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />