Had one on my 997.2 C4S but sold it as I wasn't convinced it made much difference on the gen2 PSE like it does on gen1. Think it would on my GT3 between 1-3k rpm but don't really want to fork out for another new one, would be interested in one that isn't needed any more.
http://www.carnewal.com/products/P87/p97084/PSE-Manual-Control
http://www.carnewal.com/products/P87/p97084/PSE-Manual-Control