Make sure you don't use the end seals that come with your intake gasket set. Just use a 3/8" bead of silicone. Also, make sure your valve cover gaskets are on properly. There isn't much pressure up in the heads except for the push rods. Everything else is drain back.
On the left side are a few pressure ports. Usually with plugs or the sender. You also have the filter on that side. Make sure all your plugs are tight.
Sometimes your mirror will show some assembly residue. One way to find the leak is to dry everything with a degreaser, then run the motor through a heat cycle.
