[thstone]

From my experience on the track, I would suggest that the base Boxster calipers are more than sufficient for track use; there is no need to upgrade to the "S" calipers.

Instead, use the money to install a more track-oriented brake pad, replace the stock brake fluid with a high temp brake fluid, and install the larger GT-3 brake ducts. Oh, and pull the brake wear sensors from the pads and tie wrap them up and out of the way to avoid melting the sensors.