WARNING: This page is about a different car, the 2005 Mazda MX-5 Miata. However, it is still accessible from the selected car via links, so may be relevant.
Install the intake manifold gasket with the convex side of the gasket facing the intake manifold side.
Fig 1: Installing Intake Manifold Gasket With Convex Side Of Gasket Facing Intake Manifold Side