Redline SI-1 injector cleaner, continuously per their dilution rules (1 bottle per 100 gallons of gas). I buy it by the case of 12 bottles, takes me about 18 months to bore through 12 bottles.
Over the past 19 years, I've run 4 cars on this plan, three of them well past 100K miles each, I've never had injectors cleaned, and I've documented on two of my cars that SI-1 will remove previously accumulated intake valve deposits and keep them away.
YMMV.