power steering expertise needed?

hi, and good to be back (in a way) and thanks in advance
2000 sts 145k
my powersteering pump has been leaking for quite some time and i have finally decided to have my indy replace it yesterday, and now it is worse with some funny symptoms.
my steering has always been a bit harsh to turn but i could deal with it.
now with the new pump it is worse. while waiting at a red light i turned the wheel back and forth and could feel a noticeable pulsation or chatter. then after getting coffee and pulling out i heard a noticeable squeal (one time only) the 45 mins of hwy driving and im pulling into my parking space and no assit whatsoever. i also could smell a burning odor from the pump. let the car sit for 3 hours and drive it back to my mechanic. ( he is putting on a new pump again on monday)
why or what would cause this pulsating or chatter felt in the steering wheel at standstill? and could i fear the worse that it is the steering rack itself? ( it has already been replaced a few years back) any thoughts? thanks