I use Permatex Ultra Copper. I run a bead around each of the ports on the head, and the front and back where the straps bolt down. I then also run a bead around the "ports" on the valley pan itself, where it will mate to the intake. I install the intake, put thread sealant on the bolts and tighten it up. After I warm the engine up, I go back and retighten them again. I'm running an aluminum intake and heads and have had no problems with oil leaks.

I tried the gaskets on each side of the pan and it did nothing but jack my intake up and throw the bolt alignment out of whack.