Does it "creak"/grunt in response to simply turning the wheel? The '97 D90's have a grunting when the steering wheel is turned to the left. It is caused by a harmonic vibration (of the PS fluid movement) due to the steering fluid hose lengths. LR had a fix, a long time ago, to change out the hose to those who "whined" about it.
Since it's a new install, you may just have air in the fluid still. Try turning the wheel a full crank to the left & then a full right a few times to possibly purge the air out of the system.