If leaking at the bottom persist carefully check the following areas:
Head to manifold alignment(top to bottom)
Head to manifold angle and gasket thickness that's required.
Manifold to block rail spacing(make sure nothing is holding the manifold up)
Head intake surface flat and not cut at an incorrect angle front to back,Check same for the intake surface.
Make sure there is no warped surfaces.
The angle and straightness can be checked buy using four block(steel) guages at all four corners then check all the areas at each port for discrepencies and if the four corners don't set tight on the corner guages then you know something is out of square.
We usually use 2"X 1"X .060 thick block steel guages at all four corners and check for the manifold setting flush on the guages and then pass a aluminium welding rod flattened to just a hair under .060 through the port area to see if it's loose or tight in any one spot.
We never use any torque values when tightening the intakes but use a sequence of side to side and repeat till there is no more bolt rotation with a 1/4 drive then we repeat it after the engine has heat cycled a few times.We also recheck them every few seasons if the engine sets for long period of time.