I have not yet run mine, as I am testing other options first, and have very few passes on my car. The guys that I have talked to recommend a spacer between the lid and the bottom, a 1/2" or more.( more plenum?) Also to fill the lower areas with epoxy to prevent fuel puddles. There are additional mods to be done to the inside as suggested to me by a Moparts member that had done extensive testing of this manifold.
Herb McCandless told me they did very well on the dyno, but failed on the track !?
I added two NOS pop off valves to mine as they are notorious for back firing and cracking the lid.

Mark