Are you certain your system is bled completely and free of air? Some systems have high points that like to trap air and make bleeding a pain. An air separator tank setup can be nice to make sure and they're pretty cheap on ebay.

Hate to go there on such a new setup, but what about the headgasket? If it's only doing it at the track maybe you have a head gasket sealing problem under boost/wot. Maybe try one of those hydrocarbon test strips.

*edit /\/\ beat me to the punch, haha.