When I got my oil change I decided to get a fuel injector cleaning as well. The guy hooked this can of some kind of cleaner to one of the tubes connecting to my fuel line. Firstly, I dont think he attached the can to the right hose, he attached it to, what I think is the fuel pressure regulator tube, it wasnt even screwed on, it was easily pulled off? (When the engine was running the tube was sucking air)Do you think this line feeds directly to the fuel injectors? If someone can supply a picture of the engine, I can be more specific.

Plus I'd like to replace my fuel filter myself this summer. I read in another posting that I should remove the negative wires from the battery before doing the change. Can someone let me know why? And what steps i should take before and while replacing my filter. thanks