with the tune and since he does have a full exhaust..and when u switch the heads to PI from non-PI the compression risses some and u get a lil more. If he had cams in the heads.. probably 290-300hp.. my 02 GT in sig makes 315 and 335tq.. I have comp cams in mine also fully ported heads..with a mild tune. my guess 275.
i have a 00 gt thats got comp pi cams on a non pi head intake acuufab 70mm tb/plenum - rear cats 3.73s centerforce 2 ,and a tri ax,sct tuned made 268rwhp and ran 13.9's in the muggy louisiana nights on nitto d's