That thing where hoses attach to steering gear is called Valve Body; it is fastened by two bolts to the steering gear, and where fluid passes into gear there are two small “O” rings under it. Centering of this housing or valve body corrects for self-steering.
To adjust centering of steering wheel is simple.
Start engine.
Center valve body until self-steering stops:
Back off both bolts just enough to allow movement along axis of steering column on steering gear housing. Gently tap on head of valve body to move valve body up on steering gear, and tap on end plug to move valve body down on housing until wheel stops self-turning. Taping up makes wheel turn one way, down the other, and you may have to restart engine several times to be sure centering is successful. Tighten down bolts. Expel all air from the unit by turning steering wheel full left to full right several times.
If you develop a leak from performing this adjustment, Rock Auto has a seal kit for the valve body.