As for the fuel injector cleaners, the gasoline that's made today has additives in it that do very well at taking care of keeping the injectors clean, and unless your supplier of said gasoline has questionable storage and/or transfer facilities, there is no need to spend any extra money for them.
I worked for Chevron for twenty years making gasoline, avgas, jet, diesel, and various other fuels, and I'm not promoting Chevron here (no interest), but the reports that I've read indicate that Chevron's additive that they market as "Techron", is good to use if you don't use Chevron gasoline regularly.
There are different additives blended into the gasoline from the major oil companies, such as Techroline which is used in Chevron gasoline. There are also additives available from those same refiners, such as Techron Injector Cleaner, which is an injector and fuel system cleaning agent, 100% full strength, to be mixed with a full tank of fuel. Each refiner will tout their own as being the best, so go with whomever you choose.
Chevron gasoline with Techroline is nothing more than an additive to help clean your fuel system and to help keep your injectors from getting clogged. If you use Chevron gas on a normal basis, you don't need to add a can of Techron to your fuel at every fill-up.
If you do not use Chevron all the time, use a can of Techron every 3 months/5000 miles or so, as a preventative measure against refiners that do not offer a cleansing agent as Chevron does with the ingredient Techroline.
Hope it helps you guys with the additive thing.
_ken