Below are some pictures from the L92 Truck Intake Manifold series. 

The L92 gets a great deal or work done to the plenum inlet to increase it to a nominal 90mm bore all the way into the center of the intake where it then opens up to feed the runners.  In stock form only the first inch is 90mm.  Opening up the intake in this fashion assures maximum flow from a ported TB to help feed each individual runner.   The runners are squared up, widened, and the interior roof is raised at the injector boss.  All intakes are ported with air tools using various cutting bits and a two stage sanding process followed by a high speed polishing stage.  All of this adds up the the best possible intake to feed your new L92 cylinder heads- whether a truck retrofit or new vehicle installation.