Vacuum Leaks-type 44 TQ

[HOUSTON]

Can anyone tell me where the most common vac-leaks are on this car?  I
replaced the O2 sensor, valve cover gasket (rubber type), T-shaped hose
atop the valve cover, fixed the air intake wiring(F/C 2322), and cleaned
the ISV,  yet I still only get a 1.1 boost reading.  I have not replace
the Cat. Conv. yet, but that's next.  Is there anything else that can
give a low boost reading?  There must be a leak somewhere.  Please, any
help is much appreciated.

Houston