Back several months ago I purchased some gas with water in it, the dealer replaced the entire fuel system, line etc. Now when I am idle my car shakes a little, not a lot but you can feel it shaking and making a sisssing sound, I carried it and had it put on the computer and no bad sensors were detected, they suggested I use fuel injector cleaner

If the fuel injectors need cleaning, that is best left to a professional who has access to the necessary cleaners and tools.
Working with modern fuel system under pressure can be serious business. If you're not using all precautions, you could be inviting disaster. Please be careful.