If I crank the wheels all the way either direction the power steering pump makes a clicking noise, when I'm at a dead stop and need to turn the wheels I have to power brake to help the power steering pump kick in so I can turn the wheel, and lastly if I'm coasting into a turn I have a hard time turning the wheel as the pump seems not to be assisting me with steering so I tend to take turns with my foot into it a bit. This all leads me to believe my power steering pump needs replacing (although please correct me if I'm wrong..) So my real question here is, which pump do I need? Autozone has 4 different ones listed (and ACDelco 2) on the website for a 2000 silverado 5.3 w/4WD. With or without a resorvoir and with vacuum booster or hydrobooster? Thanks guys!