at operating temp the truck stumbles at idle

What is your question?

I have a constant low vacuum at the EGR valve less than 5 Hg at idle, which it seems is enough to move the diaphragm in the ERG valve. I replaced the EGR solenoid, and I have voltage at the solenoid plug. However if I disconnect the Solenoid plug I still have vacuum at the EGR. I removed the EGR vacuum hose and plugged it, put a vacuum Gage in the system at the intake manifold I get about 17Hg. Reconnect the EGR vacuum line and it drops to about 15Hg. I am stumped