You have the GTP brakes, NOT the Big Red (aka 993TT brakes). These have a fair amount of built-in front bias and along with the front Sport Bilsteins (too much front bump valving), aggravate the propensity for front lockup.
These are really nice brakes that may simply need the addition of a Tilton manual bias adjuster (lever style) into the front brake circuit to provide the adjustability you need.
Before you do ANYTHING, make sure the factory rear brake pressure limiter thats standard on all Carrera's has been removed.
There are other things to do as well, however I cannot offer anything further without knowing something about your driving skills and experience.