The most reasonably priced component used on the Civic 2003 (3) 4dr Ex (ka) Exhaust Manifold (vtec) is the Nut,flange,8mm.
A sample from the products for the Exhaust Manifold (vtec) include: Mnfld Comp,exh, Gskt,exh Mnfld (nas), Cover,exh Mnfld, Bolt,flange,8x22.
With three applications this Nut,flange,8mm is the most specified part.