Stop in for a cup of coffee
Its built into the EGR valve itself. Put vacuum on it with a hand pump and I thought the valve was bad. But the vlave won't move unless there's some exhaust air flowing. I tried to recreate this with some shop air but it didn't work too well. Learned this all after I had bought a new one (which was an incorrect replacment) and was testing some other old ones I had. Someplace in the shop manual I stumbled across this fact.