The EGR valve should hold a vacuum when applied by a handheld pump.
Example
This is the pump I used
I just put on a new EGR valve. I tested the old one after I took it off the truck. The valve wouldn't move when a vacuum was applied and it was stuck partially open. Unfortunately the truck still idle's badly but the other tests on that first link now work correctly.
I forgot to mention earlier that the fuel pressure tested good.
I did my best to spray around the head gasket but didn't notice any difference. If the gasket was leaking, how noticeable would the change in RPM be?
What else could I try?