Seems like you guys are on it. smoke at start up is valve seals, vacuume is highest at idle and 100% load (top speed drag limmited) about 18 "hg.
A plugged EGR will cause oil to push most every where; rings, seals, and valve seals.
Rings will cause smoke under accell and plug cats and EGR's.
It seems you guys are forgetting that although absolute manifold vacume is highest at idle the venturi effect of higher intake speed at higher RPM can cause a higher realitive manifold vacume at the valves.
If when you did your compression check you didn't squirt a little oil in the cylenders you should check and compare. Goes like this, for each cylender take a "dry" compression reading then squirt a little oil down the spark plug hole. the more significant the change in readings the worse the condition of the rings.
Valve seals are cheap but labor intinsive. NMc