2008 Mustang Gt - No Steering at High RPM

I have a 2008 Mustang GT that has been turned into an SCCA T3 Racecar. Took it to it's first test day, and first session the car ran flawlessly. Second session, the car developed a power steering issue at high RPM. Anything below ~4800RPM, and the power steering works fine. Anything above ~4800RPM, and the steering cuts out completely. It doesn't just lose power steering, but goes into complete steering lock. Steering resumes once the car drops back down in RPM. The rack, pump and lines were original with about 35,000 miles on them. Flushed the system a dozen times, and replaced the pump, but the problem persists.



Any ideas?