[brucepick]

I don't know if this if true for most or if it is just a Honda thing:

EGR system feads into a set of passages in a 2-piece aluminum casting, which is a kind of mini-manifold that feeds to the intake system. The 2 pieces are like a clamshell - you take off the top piece which exposes the lower one with all the passages cast or machined into it. Clean the passages and the small ports leading to the intake and reassemble. On the Civic it's below the injector rail.