>one has holes (14057017) between the runners and one >> doesn't (14031372); these being the casting no's for what I >> beleive are 82/83 Camaro/Firebird 305 manifolds. > >They perform very differently!!. Bruce please tell us more, I recently replaced my "holes" in runner manifold, with one that had no holes. Which is suited better for what? (I've got a 5.7L). Thanks Ross Myers