You can read about user issues with these by searching FreshAlloy. They call them Freddy manifolds. Some people's have been so bad that they vacuum leak through the actual walls of the manifold. Others just complain about the casting flash and roughness.

A short runner manifold in general will help you keep your torque level in the higher RPMs. This is something that works best with cams, and after you've done all of the other accesory mods.