Also when you install the gasket you will have an option on sealing off the coolant passage to the manifold. If you leave this blokage in place you can quite possibly cause your self some headaches later.

What I mean by that is, is that if you live in a area that has a cold climate during the winter it may cause your throttle body to freeze or stick shut. The coolant is present there to keep this from happening in cold areas.

So unless you live in a region that is typically warmer than 40 degrees farenheit I wouldnt leave that passage blocked. I would cut out the flashing to allow coolant flow to prevent this problem.