[The Radium King]

yeah, initially I would think that using the oem plenum would be a bit of a buzzkill for performance improvements. I would anticipate an increase in throttle response, but no flow improvements at any rpm for 996 applications (of course, you could use an x51 intake, but big $).

on a boxster, however, you would be using a 996 manifold designed for a 3.4 on the smaller 3.2 engine, so some benefit there (regardless of itbs or no). further, the 996 manifold is taller, so longer venturis, so assume better low rpm performance, along with throttle response.

the other concern is the obstruction to airflow multiple butterflies would introduce into the system vs the one large butterfly we currently have, unless we went with aftermarket itbs vs repurposing the intermediate manifold piece.

yet another concern is where would we get vacuum for the aos, fpr and brake booster? the only thing I can come up with is a bracket where my ac pump used to be, for mounting a mechanical vacuum pump and running an aftermarket aos. this starts to become a lot of work. with a mechanical vacuum pump you now have the opportunity to add oil pumps, however ...

the more I think about it, the more i am drawn towards keeping the one tb, but still going with an alpha-n scheme (and piggyback for fine tuning). this lets me get the maf out of the airflow; improves airflow, removes a failure-prone, expensive component from the system, and adds tuneability.