It is my understanding that the gas companies already put something in the gas to keep it from breaking down. I think the amount they put in depends on the season. Sta-bil is still suggested.

The real problem here is keeping the gas from going bad inside the fuel injectors. Don't use a chemical specifically used for cleaning the injectors unless your plan is to burn the gas tank down and actually clean the injectors. Instead use something that prevents the gas from breaking down by using something like sta-bil.