The semicircular groove at the back of the intake journal is the groove for the EGR, which is packed solid with exhaust soot. It sets a code for "insufficient EGR flow" and can cause the engine to run hot, or even damage the pistons, so it has to be cleaned periodically. Engines with a plastic intake don't suffer from this.
See this pic for the PN for the gasket.
http://www.supermotors.net/vehicles/registry/media/190433 
