I have one off of my car, the most vacuum I could get it to hold was 22.5 hg. It held the vacuum pretty steady. The diaphragm starts moving long before then. I'll even include with it the black decorative cap. $30 shipped. Paypal accepted.
I have one here as well. Im pretty sure its good, my intake wasn't made for the EGR Valve but it was brand new and on there for inspection purposes with it just resting in its place...