"faulty air intake boot?"

I wish.  I have thoroughly inspected the boot several times and have not
found any problems.  the rubber looks good and strong, no cracks or dry
rotting.
By plugging the air plenum at all ports and monitoring the vacuum I have
eliminated the possibility that the aux air reg, brake booster, dec valve,
FPR, or EGR valve have leaks.  I still need to inspect that gasket between
the throttle body and air plenum though.  I have doused it in carb cleaner
and gotten no response in the rpm so I doubt it is leaking, but....Is it
possible that the air plenum itself has developed a leak along the seam?
Seems pretty far fetched.

thanks for the suggestion, keep em coming

Jake