Intake manifold leak detected. Low vacuum 10-11" hg you say. It's time for the "bucket test" and the PCV test.

PCV TEST: Unplug the PCV valve from the valve cover - plug it off, and plug off the PCV vent in the other valve cover. Start engine. After 30 seconds, unplug a side, and look for positive pressure blowing out. If there is vacuum, the intake gaskets are leaking at the bottom of the intake ports, probably sucking up some oil also.

BUCKET TEST: With the engine running, pour water onto the intake manifold and see if it causes misfires and rough running. If there is a change, the vacuum leak is real, and should be either the injector O-rings or the intake gasket leaking on the top of the intake ports. Try to pinpoint with a squirt gun if you like.

One last thing. Did you ever use the eehack software to run a power balance test? You could also unplug injectors at will and check the RPM drop. Then tell us which cylinders test weaker than the rest.