The Blacktop has an inner form from the manifold in a more of the heart form in comparison to the Silvertop’s circular inlets (see “Throttles”). The Blacktop inlets at The top facet also are wider to allow for the much larger inlet ports in the head. You should see “Throttles”, https://paxtonsrpnk.laowaiblog.com/33566075/what-does-4age-20v-itb-mean