This has been debated quite a bit. I can tell you that the secondaries are needed for N/A engines at lower RPM's. The reason for this is the "swirling" or tumbling effect. If you have the secondaries open, or removed, the air wants to travel through the larger chamber and not through the primary. Now, some of it does go in the primary, but not as much as if the secondaries where closed. Since there is not much air to swirl with the fuel, it doesn't mix properly. The fuel isn't as suspended in the air. This will cause the engine to bog a little when you have a WOT condition at low RPM's, then it picks back up around 3000RPM or so.
However, if you have a turbocharger shoving more air into the primary and secondary runners even at low RPM's it might be enough to properly swirl the fuel/air with the secondaries open/removed.
Funny thing is, the SVT owner that is getting the first kit put on is itching to remove his secondaries. The kit will be developed with the secondaries in place for consistant results. Then later, we will remove them and see what happens.
-Chris
