Mike,
Check the bottom of the intake manifold for a crack or a casting pit that goes through into an intake runner. An intake vacuum leak check could have been done before the intake manifold was removed. It wouldn't tell you where the leak was, but it would point you towards or away from the intake.
I hope that's not a crack at the lower left of your intake port.
John
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.