Just wondering if the pads were smooth and the rotors were grooved. Sounds like everything is groovy.

I would check the thickness of the rotor and if you have more than 50% remaining, get a real track pad like the HT-10. The HP Plus is a superb autox pad because it has great characteristics for braking at autox temperatures but it will not live forever on the track. Once it over heats, it's glazeville all the way to fadestown. Check LPIracing.com for the best Hawk prices I've seen plus free shipping. Run the HT-10's on there for a week of street driving and see if it doesn't "clean" your rotor races and get you smooth again. Then run them on the track and see if the rotor situation improves. If not, get a new set of blank rotors and try again with the HT-10. The HP Plus are ok for light cars and low-hp cars, not really what you have there.

Good luck and post back!