I have a 6 cyl, but the intake manifold gaskets for the 3.4L are similarly bent like that. I made sure that the gasket was symmetrical facing either way (it was) and then I put the flatter outside section facing the bottom. My logic was gm exhaust manifold gaskets have similar bends, but the gm ones are labeled for the outside flat section against the cylinder head and the bent portion goes towards the exhaust manifold. I'm not sure it would make much of a difference for intake gaskets, but I haven't had a problem with it since they were replaced a couple years ago.

EDIT: By flatter side I mean the outside edge portion mating with the head and the inside raised portion toward the intake manifold. I hope that makes sense.