Bruce,
Just to reinforce the intake gasket thing, here's a reference to that very common Fel-Pro problem:
Intake Gasket Trouble
So if you have the non-reinforced Fel Pro intake gaskets, you can expect to have the problem again. Retightening the intake manifold will probably only hasten the recurrence.
If you have the Reinz or the new reinforced Fel Pro gaskets, there should be no need to retighten.
I hope you have the right stuff installed, and no more problems!
Tom