At the front where the hydraulic line bolts to the lift, there is an oval-shaped valve with 2 flat sides. Bleed air out there with tractor running until a steady streanm of oil comes out. Do it at idle and crack valve open slightly. Tighten and see if that helps.
There is a "magic washer" behind this valve. That is what it is called at the dealer. It may pay to change it. Also, there is a "responsiveness lever" on the right side of the lift near the front, just over 1 inch long. Turn it counterclockwise to increase hyd, flow and clockwise to decrease it. Turn it to open it all the way. if your lift raises the implement them jumps up and down, back off of it a little until it is steady.
What kind of oil did you put in it? Most hyd. oil or universal tractor fluid is ok and even 30 wt non-detergent oil. You do not want any thing in there that will foam. Hope this helps.