Maintaining all the filters in front of the injectors...
I have an early build yamaha 4 stroke, circa 2000. At the time, Yamaha did not require a spin on water fuel separator for initial installs / factory rigging. They made that change many years later, and the install of one takes care of most injector issues after they are cleaned. In my case, it was the install of the spin on, regular replacement of the spin on and internal small filter, and the VST filter done when I cleaned the injectors. No issues since.
Regular use of marine stabil and seafoam is the rest of the normal routine here...