Can not stop oil from leaking.

I never use the cork, just a thick bead of sealer. On the front passenger's side the block surface sweeps back toward the rear of the car. If the bead of sealer you laid down did not sweep back on the front passenger's side it will leak. Best approach is to glue the side gaskets to the head and lay the manifold down and eye up how thick that bead should be. Then cut the applicator accordingly. I also clean the surfaces with Brake Parts Cleaner and fresh paper towels to make sure no oil residue is present.