Actually the biggest gains from porting come from the runner ends in the plenum area, which unfortunately requires the thing being cut in half. Look for posts by NA SVT on various message boards, he's the C head manifold porting guy.
The Cobra lower was a recall fix on the existing 99 flawed casting , the Mach 1 intakes refined the process where it wasn't as extensively needed, they actually flow quite a bit better right out the box. 290cfm per runner vs 242cfm for the "fixed" Cobra.
I'll buy the upper lid with the Cobra emblem:nod: