Yes and no. Almost two decades ago Toyota, GM, BMW and Honda formed the Top Tier Consortium, a trade group focused on certifying gasoline with detergent standards that were suitable for modern cars. In 1995 the US EPA reduced detergent requirements and the resulting gasoline was fouling injectors, valves, and combustion chambers. If a car uses top tier gasoline regularly fuel injector cleaner is not needed, ever. If the car gets a steady diet of random gasoline fuel injector cleaner is not enough to keep up with the deposits, especially on intake valves and - worst of all - combustion chambers. The first source has a list of current top tier brands.

Go to an automotive store, and ask for Lucas oil fuel injector cleaner. I did that on my 99 dodge ram and it worked wonders

Not if you buy a good quality of gasoline that has extra additives in it like Shell, Mobil, Texaco, Phillips 66, BP and other quality gasoline companies.

Yes. They help to keep the motor running good.