Power steering issue

Did you have this problem right after you had the new rack put in? Sounds like the bypass valve in the PS pump is bad. Try , at an idle, turning the steering wheel all the way to one side or the other and hold it tight. You should be able to hear the pump bypass. If not, then raise the rpms to where the power works and do the same thing. here you should hear the pump bypass. If you hear the pump bypass, you either have a weak pump, a bad bypass valve in the pump, or both. Hope this helps.
Could also be an issue with ehvariable poswer stereing actuator on therack and pinion.. see below

Variable Effort Steering System Description and Operation
The Variable Effort Steering (VES) System varies the amount of effort to steer the vehicle as wheel speed changes or lateral acceleration occurs. The Electronic Brake Control Module (EBCM) controls an actuator located in the steering rack and pinion. The actuator consists of an electromagnetic coil and a normally open pintle valve. The valve regulates an orifice that bleeds inlet pressure through a return passage to regulate the amount of pressure available for steering assist. The EBCM commands current from 0-1 amp to the VES actuator which varies the amount of effort required to steer the vehicle. At low speeds, 1 amp of current is commanded to the VES actuator and the pintle valve is fully closed which provides maximum pressure and maximum steering assist for easy turning and parking maneuvers. As speed increases, current is decreased and the pintle valve opens the orifice, decreasing available pressure providing firmer steering (road feel) and directional stability. The VES system uses the steering wheel position sensor input to calculate lateral acceleration during abrupt driving maneuvers. The system also uses the Antilock Brake System (ABS) wheel speed sensor inputs to determine vehicle speed. The EBCM is constantly monitoring these inputs to achieve the desired current to the VES actuator. The EBCM has the ability to detect malfunctions in the VES actuator or the circuits to the actuator. Any malfunctions detected will cause the VES outputs to be disabled, and the actuator will return to an open state. The EBCM will command the Driver Information Center (DIC) to display the SERVICE STEERING SYSTEM warning message via a class 2 serial data circuit.

Check out this guide, it will help

https://www.2carpros.com/articles/power-steering-problems

The pressure hose is a known leak, it can also develop a leak in the rigid lines that run to the auxiliary cooler. There is also a possibility that the line seals at the gear can leak.