[toddalin]

I run the Performer RPM with a 1/2" open spacer. My mechanics used to say that the spacer is better than the cut down divider because it adds plenum volume and is easily "reversable." I also blocked off the heat riser and made a "lifter valley splash shield" to keep the hot oil off the manifold's bottom.

It is also port matched and the interior walls and divider were hand "contoured" to remove casting flaws and bumps. I would bet that it now flows as much or more than the air gap.

Even more "blending" was performed after these pics were snapped. (I can get anal about such things.) It only takes some sandpaper and time.