Really? My ABF is 165hp and I've got 288mm brakes up front with Mintex M1144 pads and standard sized brakes at the rear with Mintex OEM pads (I don't run ABS either) and goodridge braided lines all round and I feels the stopping power is not sufficient. 312mm brakes should have been standard on the 16v and VR6 I reckon 
this doesn't sound right to me mate. Maybe something wrong.
when my abs packed up I locked the rears at 120mph. Standard rears and greenstuff pads front grooved disc's. The brakes were cold, but once warm is was better but I also locked the front at 90mph, well one front wheel due to diff. The abs was sorted after that

had toyo t1r's and it had new master cylinder fitted same time as the brakes. 288 setup
bigger disc just spread the heat so it takes a lot more before fade