Talk about total stabs in the dark. The Hyundai MDPS system does not have a steering pump nor does it have any fluid. It's an ECU that receives signals from a steering sensor that hen controls a motor which turns the wheels.
Seems like you bought your self a lemon since you had the problem from new and it was never really solved. While it was in warranty you should have stood your ground to fix this issue for once and for all.
Could be anything from the ecu needing a recalibration, bad steering sensor to a wonky motor. Find yourself a Hyundai specialist who knows this system well and have him look at it.
.As you can see majority of the people haven't even heard of this system and giving you all sort of bum advice about steering fluids and pumps.
First thing would be to get someone with a Hyundai specific diagnostic tool, none of that standard OBD crap and see what errors the system is giving you and then check the readings to see of everything is in spec.