You should have the ABS system checked out by a PORSCHE mechanic, the traction control part of the system may be out of synch with the braking system and related components...also I would recommend that you try a set of BF Goodrich G-force T/A high performance radials for your PORSCHE...They are sticky at high speeds, and give you good traction in real high speed cornering and maneuvering on the asphalt,.. they help quite a bit with braking under high speeds as well.