Watch this video then decide if "proper" fuel injection cleaning isn't beneficial.
BEFORE; you'll notice each injector sprays a different quantity of fuel.
AFTER; not only are the spray amounts more equal, but they're spraying more fuel during the same 30 second time. This = increase performance and economy.
Most dealers clean fuel injectors the same way you do. They put an additive in your fuel. Have your injectors tested and cleaned with an ultrasonic cleaning device. Cleaning solution is ultrasonically pulsed back (opposite direction than the injector normally sprays) up through the injector, dissolving and removing any carbon build-up on both the inside and outside of the injector.
Just my 2 cents.