Once you have finished whatever it was you needed the plenum off for, re-install it with new gaskets. I replaced the upper to lower plenum gasket, throttle body to plenum gasket, IAC gasket and EGR gasket. You should replace ALL of these while you have the chance. I paid $10 for all Fel-Pro gaskets. Then reconnect everything, check your coolant level as some will have spilled when you undid the coolant lines to the throttle body and reconnect the battery terminal. Fire it on up and check for leaks.
In the video I was checking to see If I heard any missing indicating a fuel injector issue as I had just put new ones in. They worked on the bench, but had not been flow tested. All worked well and the swap was a success. For more on WHY I swapped them, read this:
http://www.ford-trucks.com/forums/1228757-ev1-injector-revamp-and-install.html 
