The part with the o-rings is called an EHA electro hydraulic actuator, the orings do leak at times.(next to fuel distributor under air cleaner cover).If replaced, lamda needs reset/adjusted.
If it were my car, I would pull the fuel pump package cover off and take a real good look at the rubber fuel hoses and banjo fittings going to and from the fuel pump, sometimes you can't see what's lurking under that cover.
Should be 3, 10mm plastic nuts holding the cover on.
Good luck.